4WD modifications can really hurt your fuel economy

Whilst in Port Augusta filling up with water, a bloke walked over and we started chatting about 4WD accessories, and he points to his new Mitsubishi Triton that’s got bigger tyres, steel wheels, a big canopy, swag on the roof and a number of fairly common accessories.

He says its gone from 8 – 9L per hundred kilometres to 13 – 14L since doing the modifications. He went on to ask what we get towing our Reconn R2, and I said somewhere between 13 and 16L/100km, and we chatted some more.

Isuzu Dmax and Reconn R2
Our Dmax and Reconn R2 heading into the ranges of the Great Ocean Road

Modifications cost extra in fuel

A lot of people don’t realise that once you start decking a 4WD out with gear, its going to use more fuel and in many cases, a lot more fuel.

If you have a blank canvas, or 4WD with minimal modifications, think very carefully about what you are going to add, as 4WD modifications and accessories will kill your fuel economy very badly, and some a lot more than others. I know on our Dmax, we were seeing 8 – 9L per 100 kilometres when I first got it, and it had nothing more than a factory aluminium Bull Bar on the front.

After modifying it though, we were lucky to get under 10.5L/100km, which is milder than what this bloke was getting, and towing it goes up again.

I suspect that steel wheels, larger tyres (and far more aggressive tread), roof racks and swags on top were the primary contributors, but to have your fuel consumption go up by 50% is something no one is going to be overly pleased about.

Not only does it result in your fuel costs going up by the same amount, it reduces your fuel range to a level that is no longer enough, and then you have to look at long range fuel tanks and the snowball effect of 4WD modifications just keeps going.

Navara in the mud
The more modifications you fit, the worse your economy is going to get

Are you working your fuel economy out correctly?

The first thing I always point out is that if you’ve changed the tyre size, you will have to change the way you calculate fuel economy. On our Dmax, the tyres are 7% larger than the factory ones, which means the trip and odometer readings are 7% less.

For example, if I travel 100km on the Dmax trip meter, its actually done 107km, and that will throw your calculations out. Doing it correctly (if you’ve been doing it normally) will regain some nicer figures, but it can’t fix physics.

Triton fuel economy
Make sure your fuel economy is worked out correctly

What kills your fuel economy?

The two main things that badly hurt your fuel consumption are weight and aerodynamics.


Fitting larger tyres, and heavier wheels will make a massive difference to your fuel economy. If you go from light aluminium wheels with standard size road terrain tyres to a steel wheel with a larger muddy, you can be adding 30 – 50% more weight, and your engine works very hard to make that extra weight rotate.

Roof racks on our 80
The heavier you are, the more fuel you’ll use


The moment you make it harder for air to pass over, and around your 4WD you are going to use more fuel. Canopies that stick up outside of the body profile, towing mirrors that take up more surface area, tyre tread that is more aggressive, large items on the roof, bull bars and so on all make your vehicle less aerodynamic, and will make you use more fuel.

The difference a set of basic roof racks with some light weight gear on top is staggering; you can comfortably add two litres per hundred kilometres, and even more if the conditions aren’t in your favour.

Roof Top Tent Weight
Bad aerodynamics costs you extra in fuel

Think about what accessories and modifications you do

The take away is really simple; if you are considering modifications, look at all of the downsides that can come from it. Fitting a Bull Bar can be justifiable, but it reduces your aerodynamics, sags the front springs, makes it harder to stay under GVM and the list goes on and on, and every single modification or accessory has its own merits, and pitfalls.

As a result of this, we are seriously picky about what modifications we install, and you should be too.

Swapping Bull Bars on our Dmax
You should be picky about 4WD modifications, as they come at a cost

Sharing is caring!

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *