How to calculate fuel range in a 4WD

There’s little that we find more satisfying than heading off around this magic country in a 4WD, and when you head out its hugely important that you know how much fuel range you have. In this post, we look at how you can calculate fuel range in a 4WD, and what you need to be aware of.

Reconn R2 behind our Isuzu Dmax
Knowing what your fuel range is under a variety of situations is hugely important

Why does fuel range matter?

Knowing how far you can drive with your 4WD matters for a heap of reasons. Firstly, you want to know that you have enough fuel to get to the destination that you have in mind. If you run out beforehand, it can be a huge inconvenience, and in some cases even jeopardise your health and wellbeing.

Running your vehicle out of fuel is generally not very good for it, and if its done when you are working it hard its even less good. In modern 4WD’s, the fuel is used to cool your pump, and running it low means this gets hot, and you can do damage that isn’t much fun to deal with. It also means that any gunk, and rubbish in your tank is going to get sucked up, as it all goes down to the bottom where the intake is.

For many people (especially today), the cost of fuel plays a huge role in your fuel range, and when you fill up. If you know you have enough to skip an expensive fuel station, it’s a great way to save a significant amount of money.

Cost to travel around Australia
Running out of fuel is not something you want to be doing

How to calculate fuel range in a 4WD

Fuel tank size and usable capacity

The first thing that you need to know is the size of your fuel tank, and then its usable capacity. If you have a 95L tank, there’s a good chance that you aren’t going to be able to use all of it before the vehicle starts to splutter. This is amplified if you are off road, and your vehicle isn’t sitting nice and flat, with the fuel in the lowest point, where it gets taken from.

From the factory, you will have a fuel light that comes on when the fuel tank is quite empty, and vehicles come with a distance to empty calculator. Would you run this all the way to zero? I don’t, and wouldn’t recommend it, for many of the above reasons, but it might not even make it to zero!

Since fitting a long range tank which is 140L, I made a call to find out what the usable capacity was, as I was only ever putting a maximum of about 110L in the tank, after driving around with the fuel light on for 50 – 80km.

I was told its actually 127L, so it means that we could probably do nearly 200km when the fuel light comes on. You need to know what your usable capacity is, and your fuel consumption, and then fuel range can be calculated easily enough.

ARB Frontier Tank
Our long range tank holds 140L, but its only got a usable capacity of 127L

Previous consumption

I try and keep a rough scribble of our previous fuel consumptions, so I know how it performs under different circumstances. When we aren’t towing, we get around 10 – 11L/100km. As soon as we start towing our Reconn R2 at 90km/h its normally around 13 – 14L, but if we have a head wind or we are off road, it can jump to 16 – 18L/100km.

I’ll often write down the number of kilometres we’ve done, and how much fuel we put in, along with the conditions. This might say 650km through the Flinders Ranges, roughly 50% towing, and 50% not towing, and consumed 98L of diesel.

Road back to Blinman
I write notes down occasionally to remind me of how much fuel I’ve used in different scenarios

This is particularly useful for when you do large trips, and you are heading off-road, or remote for a long period of time, and your fuel stops are limited. I know that we can fairly comfortably get 800km out of our long range tank towing all the time, which is a good figure to go off.

Calculating the range

Ultimately, the calculation you use to work your fuel consumption out is the usable capacity, divided by your expected fuel consumption, and then multiplied by 100.

For example, we have 127, divided by 16 (generally no more than 15, but I like a bit of a safety factor), which gives us 7.93. Multiply this by 100 and you get 793km, which is your fuel range.

Dmax and Reconn R2
We can do around 900km total when towing, under average conditions

We often throw a 20L jerry can in for when we are in remote places, and just as a backup, as things do go wrong. When you are paying $2.65 a litre for fuel at Arkaroola, or more than $3 a litre for fuel at Lorella Springs, being able to carry as much fuel as possible is hugely appreciated.

We’re very grateful for our long range tank, and would rate it one of our best accessories. I put it off for a long time, but it would be up there with one of the first modifications I did to another 4WD built for touring.

Dmax on the gravel
A long range tank would be much higher up on the priority list on a new build

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