Diesel vs Petrol
Last updated 1/1/2019
The age old diesel vs petrol debate. It’s been going on since dinosaurs wandered the earth. This topic is already covered in many articles throughout the internet. Why should I add to the already bloated commentary? Hopefully this article offers some unique information delivered in an original way. Each section focuses on a particular performance measure and compares the pros and cons of diesel vs petrol.
Business and Cost of Ownership
Diesel engines are more expensive than petrol engines. So in terms of initial expenditure, petrol has the upper hand. You’ll get the same car with probably more power but at a cheaper price when going for petrol. The difference is significant, perhaps in the order of a few thousand dollars.
If you’re using the vehicle regularly for long trips and / or at high load, then you can look to industry to see what costs less. Diesel is used universally in industry, agriculture, mining and power generation, both in Australia and overseas. By universally, I mean petrol practically does not exist within these realms. Whether it’s a haul truck, tractor, harvester, locomotive, generator, bobcat, bulldozer, excavator, on road truck, on road 4WD vehicle or on road transport car, diesel is the fuel of choice. Businesses exist to make profits and business decisions are based on economics. So if you’re wondering which delivers lowest total cost of ownership, I think that question has already been answered. That’s the reason why diesel has been universally adopted in business. Diesel engines last longer, cost less to run, breakdown less and depreciate less. The fact that diesel is ubiquitous in business is a pretty strong argument for it. In terms of cost of ownership, there is no need to go into specifics. Business has done that evaluation already, provided you are doing high mileage and / or high loads.
If a failure does occur, depending on the failure, it can be more expensive to get repaired in a diesel compared to a petrol, particularly if the failure is related to the high pressure fuel system that exists in modern diesel engines. So even though diesel engines last longer and the probability of failure is less, diesels can be expensive to fix. So on average the diesel will cost less but occasionally it will cost more. This is something to take into consideration, especially when purchasing old vehicles.
For short distances and / or light loads, the scale tips in favour of petrol. The small saving in running costs of a diesel is more than offset by the extra expense of purchasing it. The long life of diesel is also jeopardised by frequent short trips. The emission systems on diesel engines are also stressed and prone to early failure when used only for short trips and light loads.
Servicing and Maintenance Costs
There is a perception that diesel is more expensive to service than petrol. Servicing a diesel is basically the same as a petrol. The most significant servicing activity is oil and oil filter change. Diesel oil filters are just your standard canister filter, same as petrol, there is no difference in price. Oil for diesel engines is also pretty similar in price and characteristics as oil for petrol engines. In fact many standard oils are suitable for both. Every other service cost is basically independent on fuel type – brakes, air filter, fuel filter, differential oil, cooling system, battery, greasing points – they’re all pretty much the same. One servicing cost that a petrol engine has that a diesel doesn’t are those related to the ignition system – spark plugs, spark plug leads, ignition coil, etc. So actually diesel is cheaper to service because it has no ignition system. That’s what I’ve found from personal experience.
So where does this perception that diesel is more expensive to service compared to petrol come from? Twenty years ago manufacturers specified 5,000km oil change intervals for their diesels, probably because they produced so much soot. This tradition has carried through today despite the fact that the manufacturer’s service interval is usually 10,000km (same as petrol). Many diesel owners change their oil and oil filter every 5,000km, thus doubling their servicing costs. Some people replace their fuel filter at ridiculously small intervals, believing they are protecting their diesel engine. For some reason they think the manufacturer is under-specifying servicing requirements. Or they believe servicing more often will yield a longer operating life. Even if a manufacturer did have a philosophy of under-specifying, I’m not sure why they’d target only their diesel engines. In other words, the arguments to service diesels more frequently than specified are just as applicable to petrol engines. Check out this article for a discussion on service intervals.
I service my diesel hilux exactly according to the manufacturer’s specification, no different to how any fleet owner would operate. In my opinion, having owned both petrol and diesel vehicles, servicing costs between diesel and petrol are about the same, as long as you don’t double the frequency of the recommended service interval.
Some people have gone to the trouble of servicing their diesel vehicle every 5 minutes but have been unlucky and had injector problems or valve clearance problems or something similar. They’ll tell you that modern diesels have excessive maintenance costs. However some people with petrol vehicles get unlucky too. I think, on average, maintenance will be less on diesel. They are built tougher and generally last longer (see Longevity and Reliability section below).
Smell
I’ve heard people say “get a drop of diesel on you or your clothes and that’s it. You’ll stink for the rest of your life.” I’ve never had this problem. It’s true that diesel is less volatile than petrol and so will hang around longer. But I think you’re clutching at straws if you’re using this as an argument against diesel. It’s so insignificant. I have never noticed that I smell like diesel. There’s millions of people using diesel without complaining. Use other factors to determine your preference.
Fuel Availability
Because of diesel’s universal use in industry, mining, agriculture and power generation, it is found everywhere. Wherever there are people, there’s diesel. For example, some remote communities stock diesel only. Homesteads stock diesel only. Mine sites stock diesel only. Any remote area that needs power will probably get power from diesel gensets, so diesel will be found there. If you’re going bush then diesel is a better option in terms of availability. Having said that, most communities will have petrol so the difference isn’t huge.
Vehicle Availability
There are more cars available with petrol engines than diesel engines. The car you want may not come in diesel. The diesel variant may be a longer wait. So in terms of shopping convenience and available options, petrol is better. In terms of second hand availability, because initially most cars are petrol, the second hand market for petrol vehicles is huge. You’re more likely to find a second hand vehicle to your liking with a petrol engine simply through probability in numbers.
Fuel Efficiency
Diesel is more efficient than petrol. This is because of a diesel motor’s higher compression. The laws of thermodynamics dictate that higher efficiency can be obtained through higher compression. So fundamentally, independent of design specifics and vehicle specifics, diesel engines will be more efficient. There is no argument. It’s physics.
Another reason that diesel is more efficient than petrol is that diesel does not need to be throttled the same way that petrol does. In a petrol engine, at anything less than 100% throttle, the engine needs to work to suck air in through the throttle body. The restriction means the engine works harder on the intake stroke and thus looses efficiency. In a diesel engine there is no air throttling.
Another reason why diesel is more efficient than petrol is that diesel can run extremely lean. Petrol can’t run too lean because lean mixtures cause engine knock / pinging and extreme temperatures. Lean mixtures yield more complete combustion. More air also means there’s a greater amount of gas to absorb the energy of combustion. More energy goes into increasing pressure and less energy goes into increasing temperature. This also improves efficiency.
At high loads the lean advantage of diesel gets even bigger. Engine knock / pinging becomes an increasing problem as load increases in a petrol engine. So at high loads petrol engines need to run even richer than they normally do. A diesel engine on the other hand can always run very lean no matter the load. At high loads the mixture is maintained for peak efficiency. There is no compromise made to control pinging like in petrol engines.
Another reason diesels are more efficient is that at low rpm they deliver more power and torque. This means, for a given power requirement, a diesel engine will be revving lowing than a petrol. Lower rpm yields less friction losses.
People may flag examples where they believe a petrol engine was more efficient than a diesel engine on a particular trip, or that the difference was not enough to warrant diesel. There are variables that haven’t been accounted for when a claim like this is made. For example – loading, driving style, tyres, etc. There would be reasons other than engine efficiency to explain it.
When comparing fuel efficiency you should look at figures published by manufacturers. Although this may not represent how much fuel you will actually use, it provides the best information for comparing because the testing is based on a strict standard. Variables have been controlled and accounted for. Don’t go by some guy’s story about his petrol using less fuel then his mate’s diesel. If the manufacturer quoted figures indicate the petrol uses 50% more fuel than the diesel then you can expect that difference in real life. Your driving style, vehicle loading, combination of city and highway, terrain traveled, vehicle modifications etc will yield a fuel consumption that is not the same as that provided by the manufacturer but the difference if you changed engine types would still be consistent with the figures provided by the manufacturer.
Range
Lets say you don’t care much about the improved fuel efficiency of diesel. Maybe the lower purchase price of petrol is more important. There’s still an advantage to having a more efficient diesel: improved range between fills. For a given sized fuel tank, a diesel engine will go further than a petrol engine. This becomes more important for remote area travel. With a petrol engine you may not be able to carry enough petrol to achieve your required range. With petrol you will also rely more on remote area service stations where the fuel can be very expensive. You will also spend more time stopped at service stations and so your transit time will be longer.
Longevity and Reliability
One of the reasons for a diesel engine’s universal appeal to business is its longevity and reliability. Diesel engines last longer and are less prone to break down, particularly when short trips are avoided. There are several reasons for this. One is that diesel engines usually have lower specific power than petrol engines. They produce less power for a given engine size. This means the engine is under less stress. Diesel engines are built stronger to withstand the higher compression, so for a similarly sized engine they are stronger and produce less power, giving a doubly good improvement to longevity. Diesel fuel is self lubricating. This means the upper parts of the cylinder are lubricated by diesel, particularly on cold starts when engine oil hasn’t had time to reach the top of the engine and the fuel mixture is rich, which can wash some oil away. This small improvement in lubrication accumulates over time to help yield a longer living engine.
Diesel burns cooler than petrol which means diesel engines run cooler. This yields less heat load and less fatigue and wear due to heat.
Diesel engines usually have more torque and power at low rpm. This means, for a given power requirement, they can rev lower than a petrol engine. The lower rpm of diesel yields less wear and longer life.
In terms of reliability, one thing clearly gives diesel the upper hand – the lack of an ignition system. An ignition system does not exist in a diesel engine, completely eliminating that failure mode. Generating and propagating high voltages in small spaces is inherently unreliable. The system is sensitive to the effects of dirt, moisture, gap clearances, wear and insulation degradation. There is no way around it. High voltages are difficult to control with the precision that a petrol engine demands. Many roadside breakdowns in petrol engines are related to the ignition system. Resistance to water favours diesel for the same reason – the lack of an ignition system means splashes of water or extreme humidity are less likely to stop the engine when compared to petrol.
Diesel Injectors
Some people believe diesels are too expensive / unreliable due to modern high pressure injectors. Eventually the injectors fail and they are expensive to replace. Yes some people get unlucky with injectors, but generally injectors are reliable and, over the life of a vehicle, will cost less than the extra fuel consumed running a petrol engine. Additionally, as common rail technology matures, the injectors are becoming more reliable and cheaper to replace. Soon the injector issues of first generation common rail technology will be forgotten and this argument against diesels will no longer exist.
I’ll share my personal experience with injectors as an example. My injectors needed replacing at around 190,000km and they cost $2,500 to replace including parts and labour (I would have done it myself and saved a thousand bucks if I wasn’t travelling at the time). Using ADR fuel economy figures (8.3L/100km for diesel hilux vs 13.1L/100km for petrol hilux) I can calculate roughly how much extra fuel the petrol would have cost me over 190,000km. The difference is 4.8L/100km so the extra fuel is 190,000 / 100 * 4.8 = 9,120 liters. At roughly $1.50 per litre, that equates to $13,680. Deduct the cost of the injectors and my diesel has saved me $11,180 over 190,000km.
The above calculations do not consider my reduced reliance on remote area service stations. The long range provided by diesel means I can often wait to major service centers to refuel rather than relying on expensive fuel in remote areas. So the money savings are even more than calculated.
The above saving discounts any difference in engine longevity. Hopefully the diesel engine will last 500,000km or more. Sometimes petrol engines need a complete rebuild at around 200,000km. That’s roughly the same mileage my injectors lasted. So in a petrol engine you may be facing the cost of an engine rebuild instead of the cost of new injectors. Or if a petrol engine would last 300,000km then at the time a diesel’s injectors are replaced you could say you’re up for roughly 2/3 the price of a complete engine rebuild if it were petrol.
Power and Performance
Petrol engines generally have higher specific power than diesel engines and so, for similarly sized petrol and diesel engines, the petrol will usually have significantly more peak power. They are also cheaper to make, so that the same model vehicle will likely have a bigger capacity petrol engine compared to the diesel variant in order to keep the price differential within certain limits. So, if you want maximum performance, a petrol engine is better.
The problem with petrol engines in terms of its fun factor is that they are quite dull at low rpm. You need to rev them up to get the power. Diesels on the other hand generally have more low end torque and power. This means a diesel engine can feel more fun than a petrol engine even though the diesel’s peak power might be lower. For example you can give the throttle in a diesel engine a bit of a squirt at low rpm in second gear around a corner and it will feel fun. The engine feels strong and responsive at low rpm.
Diesel’s greater low end power also makes them a superior tow vehicle. You get more power down low so you can effortlessly tow without high rpm. There will be less gear changes and speed will be maintained better up hills.
Offroad Performance
A diesel is superior in most offroad applications. The greater low rpm power and torque requires fewer gear changes and less rpm to conquer obstacles. For very steep, uneven and rocky terrain a diesel engine allows you to go slower and with less speed variability. You can chug away at very low rpm with practically no changes to throttle regardless of whether climbing a rock or dropping down a large step. It’s easy to power through deep sand without needing to shift gears. Diesels are also at less risk of problems during water crossings. The high voltage electrical system is easily disrupted by water.
The higher peak power of petrol engines can be an advantage in some offroad applications. For example hooning around dune systems or high speed attempts at crossing muddy bogs.
Resale Value
Because of the long life of diesel engines, they generally hold their value better when compared to petrol engines. So although the initial price is more for a diesel, the gap is closed when it comes to selling and you take into account the net capital outlay. I think petrol may still have the upper hand, but not by much.
Fuel Price
In Australia in big cities, petrol is usually cheaper than diesel. Diesel is a few % more expensive, possibly wiping out any potential fuel savings afforded by greater efficiency, or does it? As an example, the ADR efficiency for a 2015 4WD petrol Hilux is 13.1L/100km compared to 8.3L/100km for the diesel. The petrol uses about 58% more fuel. That is a big difference. Even with diesel costs being slightly higher, the diesel is still significantly cheaper to run. The ADR figures may not indicate what you will actually use, but because the test is under controlled conditions the comparison between figures is fairly reliable.
In remote areas the gap closes and diesel is about the same price as petrol and sometimes cheaper. I guess it’s because of the greater supply of diesel to remote areas. So if you go bush often diesel may be simultaneously cheaper and more available.
Safety
In the military, diesel engines are preferred for armoured fighting vehicles. One of the reasons for this is the reduced flammability and enhanced safety of diesel fuel. Under anything less than ideal conditions, diesel pretty much wont burn. Chuck a match in a pool of diesel and nothing will happen. It may burn slowly if you apply very high heat, for example from a blow torch, but will most likely put itself out once the heat is removed. Diesel only becomes explosive when atomized or vaporized at high pressure and temperature. Petrol on the other hand will always burn quickly and violently. So if you’re carrying lots of fuel for long bush missions through the outback, then diesel is a safer option. Especially when mucking around with jerry cans and refueling under less than ideal conditions on the side of the road. A bit of static or electrical spark will have you quickly incinerated with petrol.
Another reason that diesel is safer is that, because it burns cooler, the exhaust system is much cooler. This reduces the chance of fires caused by exhaust contact with flammable material (for example dry grass).
Conclusion
Like everything in life, there is no perfect answer to petrol vs diesel. There is always compromise. If it was perfectly clean cut then the less favourable alternative wouldn’t exist. If you’re doing high kilometers or you’re going bush a lot, then diesel might be a better option. Otherwise the lower purchase price and better performance of a petrol may be of an advantage. If you’re towing something then diesel may be better, as it should last longer under constant heavy load and the fuel saving will be more pronounced. However in any application either option will provide an adequate solution.
If you want to commute to work and go to the shops, then diesel is definitely not the best solution. The high purchase price and extra wear on the engine and emission systems due to short trips will blow away the meager fuel savings. It’s the wrong tool for the job. A better tool would be a pushbike or scooter, or at most a small petrol powered car. If you want to haul you and your gear hundreds of km then diesel is a good solution.
I started on petrol as a city boy going for occasional camping and fishing missions. For touring around Australia I went with diesel and so far I think it’s been a better choice. Fuel costs are easily the single biggest cost when pulling huge kilometres on a tour around Australia. The fuel savings are great, and so far I’ve had exactly zero problems with the engine, other than the injectors at 190,000km.
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See also:
Emission Systems – Worth Tinkering?
Exhaust Pipes: Is Bigger Better?
Sprint Booster – Is It Worth It?
Diff Locker vs Traction Control
How Often Should I Service My Car?
How to Improve Fuel Efficiency
outbackjoe 
Good analysis, with a lot of arguments! But, in some countries, there is solution with LPG fuel systems for gasoline engines.
It turns the story upside down. For less money, you can get a car that is more powerful and fuel costs were 20 .30% lower than diesel. Prices for parts of the ignition system is significantly lower than the price of parts of high-pressure diesel. In my country, Serbia, the average owner of a vehicle with a gasoline engine thinks of gasoline as an alternative fuel. Primary fuel is a mixture of propane and butane. For those lucky ones who live in countries where they are available and methane as fuel, fare is still 50% lower than the propane-butane! Both gas and provide a longer service life of the engine compared to gasoline.
On the other hand, propane-butane mixture reduces petrol engine power by about 3% and methane by about 25%.
There is a basis for a new article, right?
Hi Dusko thanks for your feedback I don’t have much experience with LPG. I know industry do not use it in their cars, trucks or heavy equipment. If there was a saving to be made I would think it would be exploited by industry. Also LPG availability is not great, especially in remote areas. After taking into account the capital cost and the increased fuel consumption when on gas, most of the cost savings per litre are offset and I think the benefits aren’t much but I don’t really know first hand.
Taxis in Australia seem to favour LPG, so you could argue that it does have some business investment.
Yeah over petrol they favour LPG and I think taxis have traditionally always been petrol powered family cars. So they have no diesel alternative. For example if there were hilux taxis I reckon they’d all be diesel rather than petrol converted to LPG. But you are right lpg is used in industry for power generation when next to a pipe line. That’s in large gas turbines where the availability and price of gas makes sense.
Yes, you are right: availability is main problem. Fortunate for us, generally, in European countries LPG is sufficient available: for example in Germany – http://www.mylpg.eu/stations/germany .
LPG consumption is 15% more in liters than gasoline, but price per liter is about (depending of country) 50% lower. In praxis, we drive at 40% lower price, with few percent lower power! Additionally, we can keep max power by software, with immediate switch back to gasoline, if rpm/load will go over programmable limits.
Automotive industry has more interest in methane: diving costs are lowered double than on LPG or diesel! And, cars with this fuel are produced from about 10 years ago. Some of new models from Opel/GM:
http://www.motornature.com/2011/12/opel-introducing-new-cng-zafira-with-turbocharged-engine-long-range-with-carbon-fiber-tanks/
In my country, I cannot drive on CNG (methane) because availability of methane. But, I think, I will never more drive on gasoline: LPG technology help me on last 3 vehicles to spare 40% in last 460.00km ! Without problems on vehicles and any other troubles!
Interesting?
Yeah it is interesting that’s good longevity and the fuel savings are good. Gas is definitely an option. I think diesel still has some advantages.
correction: 460.000km!
Some great points Joe, but the economic decisions buy farmers & transport industry are influenced more so buy govt rebates where mr &mrs average don’t get the same deal.
Extract from Josh Dowling
Figures from the Australian Institute of Petroleum show that only 25 per cent of all diesel is sold at service stations; 75 per cent is bought in bulk by the mining and agriculture industries. Of the diesel fuel sold at service stations about 80 per cent is bought by the long-haul trucking industry which gets a 12 cents per litre rebate from the Federal Government.
The concession to trucking companies cuts their fuel excise to 26 cents per litre. The mining and agriculture industries pay no excise as they’re entitled to a full rebate of 38 cents per litre. Drivers of diesel cars pay 38 cents per litre in fuel excise, the same as drivers of unleaded vehicles.
Also in my honest opinion after owning petrol & diesel 4×4’s…modern4x4 ‘s are time bombs. Massively high pressured injector pumps on smaller and smaller motors.,injectors that can’t be rebuilt. Over a grand each one, and if you need a new pump, you nearly have to take out a second mortgage. Some car companies are walking away from warranty claims saying bad fuel is not our problem…
Diesels like to run & not short trips , petrol is more suited in this application.
I honestly think if you are a low to average km driver with the trip away twice a year..and short stop start commutes in between it may take a long time if any to reap rewards …by the way I own both …a 1993 1hdt 80 series landcruiser and a 2.7 petrol Hilux
Cheers Phil
Hey Phil so you reckon companies like Cummins and Cat are producing diesel engines for the world market because of Australian tax laws? Power generation, agriculture, transport and haul trucks are universally diesel throughout the world because of Australian tax laws?
Anyway I had look on the ATO website and as I understand it the concession applies to any fuel https://www.ato.gov.au/Business/Fuel-schemes/In-detail/Fuel-tax-credits—for-GST-registered-businesses/Calculating-and-record-keeping/Fuel-tax-credit-rates-and-eligible-fuels/
This makes sense, the tax depends on what the fuel is used for and not on the fuel itself.
Yeah the high pressure fuel delivery can be a bit sensitive. But I think it’s a bit sensationalised by upset people on the internet. For example I never heard of Hilux injector issues in 7 years of using them on mine sites. Only found out about it when I decided to get my own Hilux and started to sniff around on the net. I’m on original injectors and done 120k, fingers crossed they last a while longer. The companies with fleets keep on buying all these common rail diesels the same as they’ve done for the last 10 years so they can’t be too bad. I agree there is room to improve, I think as the technology matures it should become more reliable. Yeah agreed if you do short runs and not many km then petrol is good.
Great article. I am afemale with little experience with cars. I am about to buy Renault koleos SUV. The choice is diesel or premium unleaded. I am thinking diesel because premium unleaded is expensive. And dealer is offeringhave a really good deal on diesel withl little difference to price of petrol model. But I will be city driving mainly. I am confused if diesel is bad for short drives. A mate said that subjecting diesel engine to short driv es is bad fo r it, aside from getting no saving because fuel efficiency kicks in after min 20_30mins only.
Hey Jean I reckon both petrol and diesel will do the job for you. Diesel advantage is diminished for short trips. Yeah doing short drives and no long drives I’ve heard can accumulate soot and stuff in diesels. But long drives are better than short drives for any type of motor. Hopefully most people do some long drives every now and then. If the vehicles are about the same price I’d probably go diesel mainly for personal preference.
Hi outback Joe,
I would have to disagree about your assessment of unleaded in the outback. I have driven from Brisbane to Port headlands. Via the Simpson and great sandy and Gibson and little sandy desert and did the east and west McDonnell ranges as well. I was in a td Prado, and a mate I was traveling with had an unleaded Cherokee. We never had an issue getting unleaded, as it was available i every aboriginal village. And was was significantly cheaper then diesel.
Yo Andy thanks for your comment. Petrol significantly cheaper than diesel in the outback? I’ve never seen that. If you go to fuelwatch.wa.gov.au and check some really remote spots like derby or fitzroy crossing usually diesel is a couple of cents cheaper. Derby right now petrol is 186.9 and diesel is 182.5. Other regional centers usually diesel is a couple of cents more expensive. Not much in it unless you’re on premium unleaded which is always more expensive.
Availability is probably no longer much of a differentiator. Like you say petrol is available practically everywhere. Maybe in an emergency diesel could have an edge with remote homesteads and stuff.
Best article I’ve read comparing petrol and diesel. Thanks
You’re welcome dude
One thing that was really popular a few years ago (but I havent heard of for ages) is diesel with gas injection. I know of a few people that have done it (I wanted to but didnt have the coin) and they loved the huge extra power they got from their diesels. On the downside, there have been concerns of cracking heads…
yeah I’ve heard of a few engines exploding from gas injection. Dump more fuel in there, particularly fuel it wasn’t designed for, and failure rate has to increase. It can still be done. Companies that sell chips also sometimes do gas injection.
Hey there, thanks for a clear cut, straight forward comparison! You covered both sides without beating around the bush like most other articles I’ve read on this topic. Great help!
Cheers,
Emily.
Hi Emily thanks for your kind feedback, glad to help.
Excellent article thanks and very useful as I am tossing up on that question right now. Just to add to the comments re LPG. I have a falcon ute with dedicated factory fitted LPG. It was great when I lived in Sydney where LPG is currently 60c per/l – but I am in Gladstone at moment where LPG is 90c/l even with price drop on petrol – and when I get on the main road in QLD, only every second or third gas station has LPG. I have had some real close calls running out of LPG particularly towing a boat – on one occasion I had to drop boat off and make a run for nearest gas station 40ks away with 30ks range on the tank. It was nerve racking and I pulled in just as it flicked to zero. That swore me off LPG for good because if you run out its a tow job. So in the country not worth it
I have just purchased a Nissan Parol Y 62 which only comes in V8 petrol. The major reasons for the purchase over other 4x4s was that it was NOT a diesel. Motoring journalists keep saying that Nissan need to provide a Diesel engine. Why? Because people have been brain washed. When you look at the overall cost of purchasing and running a vehicle ( rego,insurance, etc etc etc.) the cost of fuel is insignificant and there is nothing like a V8 petrol engine. You also mentioned the smell of diesel fuel being of no consequence, this is so wrong, it is the one reason that I will never ever own a diesel car. I am really pissed off that I have to share the same pump. For some reason owners of diesel vehicles are unable to refuel without spilling it all over the ground for us petrol users to step in. Diesel pumps should be relocated away from the petrol pumps like they used to be, so we don’t have to put up with the stink.
Yeah I’ve been brain washed. And so has industry, agriculture and mining.
I guess the few hundred million dudes who are happy to use diesel are just hardened men with balls of steel, to be able to put up with such intolerable stench! I’m pretty tough myself.
Thank you for explaining the difference between diesel and petrol. I guess it would be smart to know that diesel is found in almost everything. You can use it as fuel for almost any machine out there. It also has a special engine it needs to use.
Good article. However I would question the short trips around town is bad for diesels. If you take DHL or UPS delivery vehicles they are all diesels, not petrols and do hundreds of thousands of kms doing short trips and stopping and starting the engine with no ill effects. Just saying.
Hey Dan the length of the trip is irrelevant, what I mean is minimising cold startups and trips where the engine never gets to operating temperature.
Couriers are always warm. Same as taxis. Those engines last forever.
What are your thought on emission controls on modern diesels? There’s no escaping from the fact that they are filthy engines, so manufacturers have to go to great lengths to meet emissions standards. This means introducing systems that add complexity, and create more potential failures, such as EGR systems and DPFs, both of which can wreak havoc and be very expensive to fix. Reliability and longevity definitely applies to older diesel engines, but I would argue that the emission control systems in modern diesels are more prone to failure that ignition systems in petrol motors. Also common rail diesels are becoming increasingly sensitive to low quality fuel, which is common in metro and regional areas, and can cause injector failure, or fuel pump failure, both of which are very expensive to replace.
Hey Russell
Industry, mining, heavy duty transport, agriculture – they’re still choosing diesel despite emission systems and common rail. Personally I’ve never had a problem with my diesel and I know of many long living trouble free modern diesels. Of course some people get unlucky and nothing is perfect but a lot of the negative stuff about emission systems is either people using the vehicle wrong or people addicted to changing stuff and needing to validate their efforts. I wrote an article about it: https://outbackjoe.com/macho-divertissement/macho-articles/emission-systems-worth-tinkering
Nice write up, but the modern diesel engine is less reliable than a petrol engine and that’s a fact. Diesels require increased levels of technology to meet stricter emissions standards. Diesel particulate filters are not without their own new set of problems. Injector issues are common with diesels. At 120,000km you need to swap the injectors out at a hefty price of a few thousand dollars to your service bill. Ignore this and the injectors are at a real risk of developing problems not long after the 120,000km interval and produce more carbon. This will block the oil pick-up screen and starve your top end of oil creating the “death rattle.” Not all that uncommon. The risk of blowing the engine exists. Injectors for a petrol engine are good for the life of the motor.
Petrol engines can put up with more neglect than a diesel. Don’t dare leave the oil in longer than you’re supposed to with a diesel due to carbon build up problems. Diesel engine oil has higher detergent levels in it to help combat the high carbon build up. Due to the injector boogey man the diesel service costs are higher. Also diesels suck in more air due to no regulation of a throttle and make air filters dirtier quicker than petrols and increasing the replacement of air filters also cost more.
I’d feel much more at ease taking a petrol 4wd to remote parts of the country than diesel due to reliability. Diesels are sensitive and the risk of getting contaminated diesel can cause troubles. Running out of fuel in a diesel is a big no no and not as simple as putting more fuel in it and starting it up again.
Petrol engines last a long time these days. Decent makes of 6 cyl petrol 4wd’s are getting well in excess of 500,000km with little to no mechanical problems. Usually just the normal wear & tear items like starter motors and alternators need to be replaced every 250,000km on average. The diesel equivalents during that time will be up for more expensive fixes, such as injectors, turbos and the other list of increased common problems they’re plagued with these days.
Why aren’t Diesel engines made larger to suit their vehicle size? Why are they always small engines and barely adequate? Make them bigger to actually cope with the weight of the car they’re pulling and it’ll certainly make them gain more respect from the buyers market.
Diesels also sound dreadful. That crappy finger nails down a black board constant diesel drone in an auto transmission diesel is not awe inspiring. It’s like stepping back in time (and not in a good way) if going from a modern petrol to a modern diesel. A louder engine with less power and less mechanical reliability. No thanks. I like the driving experience and don’t want it to become a chore.
Your chances of becoming a dissatisfied new car owner are increased with a modern diesel. As I said earlier, they’re plagued with a whole set of problems across the board which are common enough to be cause for concern. You’ll get to a first name basis with the dealership service manager. Buy a petrol if mechanical reliability, driving pleasure & performance is more important to you.
Haha you open with an unsubstantiated and obviously emotionally biased “that’s a fact”. Nice way to immediately throw any credibility out the window.
I guess my car didn’t get that memo on the 120,000km injector limit. Neither did industry, agriculture, power generation or transport.
Blocked oil pick up is not related to normal injector wear. It’s caused by faulty injector seals and was corrected in around 2007.
I counter your impressive arguments with this. Petrol sounds terrible like someone vomiting and farting at the same time so bad in fact that the sound has caused several catastrophic accidents. Your chances of being completely dissatisfied with petrol and having your manhood questioned and dying of a drug overdose are much higher with petrol. That’s a fact.
I would throw in that German taxis have for many years almost exclusively been diesel E Class Mercedes – with legendary longevity and reliability (admittedly taxi use is rarely the same as a personal car).
Bretts right, after 150000km youre injectors are on borrowed time. We have a fleet of v8 cruiser utes and have had 5 engines fail in the last 3 years, due to dribbling injectors, they melt holes in pistons and break crankshafts. We now put a new set of injectors in on 100000km service and auction the utes at 200000km. Dpf filters block up aswell if the exhaust temp isnt getting high enough. Some manufacturers now have adblue systems fitted, something else to worry about and an added cost. Common rail fuel system, variable geometry turbos, dpf and adblue have made modern diesels unreliable. If i was towing a HEAVY van i would get another diesel, but apart from that i will stick with my petrol.
I also thought diesels were the way to go, coming from a farm background I subscribed to outbackjoe’s logic.
What is missing in the ‘business has validated diesel as the best option’ argument may be the emissions control systems legislated for passenger vehicles. Tractors certainly don’t need it, and I am not across truck emission legislation but the torque characteristics of a diesel probably make any higher costs associated worth it.
Really the argument relevant here is what is best for the normal road going vehicle. The fact that ships use compression ignition engines doesn’t mean that it’s the best thing to drive around town in.
We bought a Patrol with the notorious ZD30 motor. A well known hand grenade. This was possibly the canary in the coal mine as far as modern diesels go. 3 litre, variable nozzle turbocharger, EGR sooting up intake manifold, PCV that coats Mass Airflow Sensor in grime (sending erroneous data to ECU, screwing up mixture control).
I think the only major component that is still original is the turbo (could be wrong, we weren’t the first owners). It has cost us a fortune. Our next car will be the 2017 V6 Hilux 4X4.
The fact that there are no 4×4 dual cabs been offered in petrol for 2018 in Australia shows that there needs to be more debates like this!
I may also be jaded. ZD30 after all
Drove from Adelaide to Perth across Nullarbor in diesel crafter. Never again. Nearly sent me broke with fuel bill. Should’ve driven ram 1500 with cylinder deactivation technology.
Such a well controlled experiment, that proves it, well done. I guess the science and the adr figures and the universal use of diesel in commercial transport are all wrong.
I did ceduna to coolgardie on one tank + 10l from jerrys, about 10l/100km loaded to the hilt for long term living, roof top tent up top.
On this road test of the ram 1500:
https://www.carsales.com.au/editorial/details/ram-1500-2018-review-114398/
they used 14.8l/100km according to the (usually optimistic by around 10%) trip computer. That was no load and mostly cruising on bitumen. Good luck with a load and / or offroad.