The best engine type for a 4WD is a diesel. No contest. There will come a time in the future where EVs (Electric vehicles) provide an adequate range for a 4WD but until that time comes diesels will remain the best power source available.

Diesels Belong Everywhere

Because of the easy way diesels produce torque (the motion that turns all the components over and drives you down the road) it is an engine type that suits a wide variety of applications and that’s why passenger cars, 4WDs, trucks and buses all use diesel.

With greater fuel efficiency and the promise of greater engine longevity a diesel makes better use of the earth’s resources.

It’s All About Efficiency 

A petrol engine is not a particularly efficient power source. Out of a litre of fuel comes only 20-30% of energy produced (this will vary marginally according to the sophistication of the maker’s engine technology). That’s not a particularly good outcome when it comes to putting your hand in your pocket, week in, week out to fuel up your vehicle. Expensive, expensive, expensive. Diesels on the other hand produce around 40-50% efficiency, a huge improvement and it translates on the road, in significant fuel savings and ease of driving, especially off-road.

Beware The Scammers

The diesel cause didn’t get a lot of help a little while ago when Volkswagen thought it was a good idea to fudge its emission declarations and they got caught out in the “Dieselgate” scandal, something I wrote about in my collaborative online magazine Loaded 4X4 in January 2018. The link to that article is here

That’s precipitated an avalanche of opposition to diesels used especially in urban environments where exhaust particulate matter might be concentrated and thus increase the chance of respiratory infection or even cancers. Those same urban areas will one day be the province of EVs, but the longer distance journeys where heavy hauling is required will still be the diesel domain.

Volkswagen took on the world’s regulators with a gamble that’s proved very costly to them, with fines measured now in the tens of billions and plenty of trust lost by customers left with worthless vehicles. There may well have been other manufacturers who tried this deceit as well but so far have gotten away with it, so we consumers can only hope that new and increasingly more stringent emissions standards on vehicles are adhered to and that spawns new technologies or improvements to achieve a cleaner and more efficient world transport system.

Remember This Acronym… CRD

Ever since the advent of common-rail, full electronic fuel injection (direct), coupled up to a turbocharger and intercooler, the negatives attributed to diesels in the past have largely vanished into thin (cleaner) air. Squirting fuel into an engine at precisely metered amounts has removed the biggest diesel bogey of the past – over-fuelling and black soot.


The Common Rail; electronically controlled fuel injectors dispensing fuel in
precise quantities under extreme pressure from a “common rail” or manifold.

Rattly No More!

Diesels of a decade ago were pretty forgettable, non-existent acceleration, rattly, smelly, and plenty of unhealthy exhaust particulates. Naturally aspirated (non-turbo), indirect-injection motors were the worst offenders and Japan produced plenty of them. Their old-fashioned fuel pumps weren’t particularly good at metering fuel in exact quantities and a lot of the time over-fuelling occurred. That was the black smoke you’ll still see on older diesel vehicles coming out the exhaust pipe. These same vehicles were pretty dangerous on the highway too, as you had to plan an overtaking move kilometres in advance, but not anymore, don’t bother dropping a gear, just mash that accelerator pedal, hang on and ride that sweet seam of torque.

Where’s Your Torque Hiding?

With a petrol engine, maximum torque is typically found pretty high in the rev range, 3-5,000rpm whilst a diesel gets cracking from just off idle, and peaks at around 2,500rpm. In every driving situation that translates into fuel-efficient motoring. There’s simply no need to rev the vehicle out beyond that point. Use the gearbox, hit the torque peak and go up a gear. Lots of 4WDs are running six-speed gearboxes these days, so it’s easy to find yourself at the highway limit barely ticking along at 2,000rpm. Lower engine speed means less fuel used. Off-road it means that you can pick your way over obstacles at a snail’s pace, minimising the damage potential to the vehicle and the track.

Big Is Better… I Don’t Think So   

There’s also been a reduction in engine size over the last few years. Gone are the big old and lazy 4.2 litre sixes that were the industry standard size, replaced with sizes ranging from 2.0 litres to 3.2 litres in four or five cylinder configurations. As the fuel systems have been refined and more and more torque extracted, engine capacity has come down. I’ve been driving 3.0 litre DMAX and MUX in recent years. With 380Nm (pre-2017) or 430Nm for newer models there’s enough get-up and go to tow and they’re cheap as chips to run. It’s simply a case of less is more.

Go Double The Distance

If you’re still not convinced, the quoted fuel consumption figures you’ll see on websites for different vehicles are often understated. From my experience driving like for like vehicles, petrol versus diesel often shows a greater disparity than the 10-15% advantage they quote. I’ve seen diesels often do double the distance, especially off-road.

If you do the research even further and investigate “cradle to the grave” costs, the cost of manufacturing the vehicle, the value it generates whilst in service and longevity, diesels win hands-down. Diesels that get plenty of TLC (clean air, clean fuel & clean oil) will happily run up hundreds of thousands of kilometres before they need a spanner turned on them.

There’s A Couple Of Considerations

Whilst I’ve been extolling the virtues of diesel power there’s a couple of warnings that need to be said. As diesels have become increasingly more reliant on electronics to meter fuel air-flow and engine temperature there’s a need to ensure they are adequately serviced.

Removal of excess exhaust particulate matter is handled in a couple of ways, either using a DPF (Diesel Particulate Filter) and/or AdBlue depending on where your chosen 4WD has come from. If its origins are European it’ll likely run AdBlue and you can read what this urea based chemical additive does here.

Some makers have better success than others in making their systems work reliably, the main objective is to maintain fuel efficiency (as fuel is used to deliver the burn to eliminate the particulate build-up in the DPF assembly) and not be left trailing plumes of smoke behind you when the vehicle does a “burn”, something at the time of writing has been noted with Hilux and Prado using the 2.8 litre 4 cylinder diesel. Another casualty is the potential to start fires on grasses that might lie close to a Ford Ranger or Everest’s exhaust pipe as their DPF sits low and under the vehicle. Do your research on this before you commit to buying and see what the experience of others has been.

Hail The Holy Grail… I Hope Diesel Hybrids Are Coming

I’m confident that storage will improve dramatically over the next few years as battery advances are made, so the range whilst running purely on electric power will increase. But I can’t wait for the day when we’re offered a real alternative and auto-makers offer diesel hybrids. Imagine that, a small diesel that’ll already average 3-4L/100kms with 300Nm of torque, coupled up to an electric motor that boosts the combined torque figure to 500Nm or more and provides a cruising range of 2,000kms before it needs refuelling? That truly would be exciting.