last updated 22/03/2016
Fuel efficiency is an important parameter when camping or touring. Fuel is one of the biggest costs of any camping trip so keeping it down helps free up significant beer funds. It’s one of the reasons I chose the Hilux. Many people are disappointed when they find out what their fuel consumption is with a loaded vehicle, stuff on the roof and towing a trailer or caravan. Unfortunately the laws of physics are a harsh mistress, and you can’t add weight and a wind resistance without consuming more fuel. When touring we average around 11L/100km – this includes significant offroad work and highway cruising speeds of around 90 to 100km/h. Most trips include some level of offroading so I don’t have a figure for highway only. Our worse tank was around 12.0 and best was around 9.5. Not bad considering what those towing a trailer or caravan are reporting from our conversations with them. A chap driving a big American ute towing a 5th wheeler reported around 33L/100km. Big four wheel drives with big caravans are getting 17 to 25L/100km, depending on variables such as type of vehicle, cruising speed etc. A Mitsubishi 4 cylinder turbo diesel was getting 14L/100km towing a large van at 80km/h. A turbo diesel Prado towing a camper trailer was getting around 13.5L/100km cruising at 100km/h. The best figure we’ve heard was from a fella traveling by himself driving an old Navara 3.2L normally aspirated diesel, towing nothing. He says he got 9L/100km cruising around 90-100km/h. Not towing anything does compromise space and comfort, but the returns are better fuel efficiency, reduced wear, increased mobility and less risk when going off road.
My vehicle has around a tonne of gear in it when fully loaded with fuel and water (that’s a literal tonne not a figurative tonne). The load on the roof rack and the roof top tent has had a significant effect on fuel efficiency, especially at higher speeds. Cruising above 100 really blows out the efficiency. At 110km/h I used to get around 9L/100km, now it’s more like 13. I prefer to reduce speed a bit – it’s better for the environment, better for the car, reduces tyre wear, reduces the stress related to driving aggressively and overtaking, saves fuel and gives you time to take in the scenery and think about what sort of beer you’d like to spend your fuel savings on at the next roadhouse bar.
I tested instantaneous fuel efficiency at various speeds on a straight and level stretch of road on the Nullabor in Western Australia. The wind was calm, the airconditioner was off, the windows were up and the elevation was 40m above sea level for the entire test. Vehicle tested is a 2007 manual dual cab Toyota Hilux SR5 3L turbo diesel (D4D). These figures are from the trip computer so accuracy is rough but still provides a good indication of how fuel consumption quickly escalates with speed.
Look at the jump from 100 to 110km/h – just an extra 10km/h consumes an extra 2.3L/100 or around 22%. At 60km/h, the motor is revving very low, well below optimum, and is so lightly loaded there is probably a greater proportion of engine power running engine overheads compared to that being used to move the vehicle. Not an efficient way to run the engine, using only a small portion of rated power. Regardless, wind resistance dominates so much that 60km/h is far more efficient than higher speeds. The effect of wind is even more pronounced if towing something. That’s why you sometimes see people towing stuff cruising at 80km/h.
So at 60km/h, fuel consumption is about half that at the speed limit. Halve my fuel costs by going 60? It’s tempting, but might be a bit annoying to other motorists, and annoying to myself considering the nagging I’d get. I hover close to 100 most of the time, but I can break the 10L/100km barrier by sticking to 90.
Our best fuel economy whilst fully loaded for touring was 9.5L/100km. It included a couple of hundred kms of gravel work and some slow four wheel driving in and out of dry creek beds on our way to Whistleduck Creek in the Davenport Ranges. The rest was tarmac cruising at 90km/h, apart from the drive from Mataranka to Darwin where the wife got cranky and we sat on 100km/h. Mind you there was a tail wind at time. In any case it’s good to get under 10L/100km.