DIESEL VS PETROL: FAMILY SUV BUYER’S GUIDE
Many, if not most SUVs, are offered with a choice of diesel vs petrol engines. But which is best suited to your needs, or even desires?
Let Gumtree Cars lend a helping hand with this guide to the pros and cons of the two types of power plant.
Diesel vs petrol; it’s a big decision and one you need to get right to make sure the SUV you choose is the right one for your family now and into the future.
Back in the early part of this century, the SUV started to get a stranglehold on the hearts, minds and wallets of family-car buyers. At the same time, the cult of the modern turbo-diesel engine arrived and people were falling over themselves to grab a slice of this exciting new tech.
And you can kind of see why: The turbo-diesels that were arriving here in SUVs were rather miraculous things with excellent fuel economy and great driveability. They were new and novelty sells.
But that’s all kind of changed now, and the familiar old petrol engine seems to be entering a new golden age.
That’s down to a few things: The VW Dieselgate scandal that rocked the car world a few years ago (and is still making ripples) turned a lot of people (and car-makers) off diesel; folks now understand the full ramifications of diesel in an emissions and cost-of-ownership sense; and, thanks to a process of Nth-degree refinements, modern petrol engines are the best they’ve ever been.
But which is right for you? Well, it comes down to personal preference, but also, crucially, the way you intend to use the car. We’ll get to that in a minute. Meantime, what are the pros and cons of each type of SUV power plant?
Let’s start with diesel – specifically the modern turbo-diesel (since all diesels in SUVs are now turbocharged).
The pros start with fuel economy. Big time. Let’s look at a popular SUV like the current Toyota Prado. While the turbo-diesel has an official fuel consumption number of 8.0 litres per 100km, the petrol version with the same transmission has a figure of 11.6 litres for those same 100km. That’s almost half as much again!
But modern petrol power plants (unlike the one in our Prado example) are often downsized in capacity terms but use the diesel’s trick of adding a turbocharger to boost performance.
Which they do very effectively, and this has sliced fuel consumption AND boosted power and torque. While a new Volkswagen Tiguan 110 with a diesel engine has a fuel figure of 5.9 litres per 100km, the petrol version is less than a litre away with 6.3 (although the latter is only two-wheel drive while the diesel is all-wheel drive, but you get the idea).
The catch between diesel vs petrol, is that not all petrol engines are created equal and some of the non-turbocharged four-cylinder examples lack the necessary oomph for relaxed driving. Make sure you can live with the performance on offer.
Making the modern turbo-diesel as good as it is has involved some seriously high tech.
Common-rail direct-injection is now the dominant technology and while it’s an effective way of making big power from a small-ish engine, it involves complexity in the form of brutally high-pressure fuel pumps, expensive fuel-injectors and on-board computers.
Because diesels are inherently dirtier inside (thanks to the soot formed as the fuel burns), on balance they need more frequent oil changes – and that means higher servicing costs.
To keep a lid on emissions, some turbo-diesels also run what’s called a diesel-particulate filter, which is a soot filter that traps some of the airborne nasties in the exhaust and burns them off later to clean them up.
These soot filters can also be a big service item for some owners (and we’ll get to that, too). And if you need new injectors (and you will) then brace yourself for anything up to $1000 per injector. That’s going to be a big service bill and it doesn’t really matter which brand you buy.
The modern petrol engine is also a bit more maintenance hungry than its predecessor, but not by the same margin. Even a turbocharged petrol is a simpler servicing proposition, and although diesels have the reputation for lasting longer, that advantage has kind of lost its meaning now thanks to those servicing costs, not to mention that petrol engines have never been as long-lived as they are now.
DIESEL VS PETROL: DAY-TO-DAY
Broadly speaking, a petrol engine is cheaper to make than a diesel, so the cheapest (entry-level) version of an SUV is likely to be the petrol model. The catch is that if you want all-wheel drive or the version with a sunroof and heated seats, you might be forced to take the diesel-engine option as well.
A turbo-diesel will (generally) make more torque than a petrol of similar size and economy and is particularly flexible and suited to life behind an automatic transmission that Aussie buyers clearly prefer in about 99 cases out of 100.
But the modern petrol engine claws back some ground by being smoother and quieter to use while offering a sportier feel to the way it produces its power. Either will comfortably sit at freeway speeds but the diesel is probably the best choice if you’re towing big loads thanks to its mighty torque.
When comparing diesel vs petrol, petrol engines are much nicer to live with, though. Aside from the smooth, quiet performance (particularly if the vehicle has stop-start technology) that even extends to filling the tank.
If you’ve ever filled a diesel vehicle, you’ll know that you’ll have a stinky hand for the rest of the day as the pump is always covered in diesel. Unlike petrol, spilled diesel doesn’t evaporate, so its stays on the pump and in a pool on the ground which you inevitably stand in and then traipse diesel into the cabin.
Getting all green for a moment, it’s generally agreed that while a diesel engine uses less fuel per kilometre, its tailpipe emissions are, in fact, nastier than those of a petrol. Oxides of nitrogen are the killers – literally – and these emissions have been linked to cancer and other maladies.
This is why the modern diesel uses a soot filter or injects urea (from a separate tank which typically needs refilling every 15,000km of so) into the exhaust to trap or clean up those emissions respectively.
A petrol engine? Well, since lead was removed from petrol decades ago and modern computer-control and design has improved efficiency, the petrol has never been cleaner.
Even though it’s better than it was, diesel is still dirty enough that many car-makers plan to phase it out over the next couple of decades. And if you really want to go green, a hybrid SUV is the way to go. And if that’s the case, it’ll be a petrol-electric hybrid, not a diesel-electric.
DIESEL VS PETROL: THE BOTTOM LINE
Here’s where the rubber hits the road when looking at diesel vs petrol: regardless of your personal preference or your willingness to put up with higher servicing costs, or whether you’re trying to save the planet, there’s one inescapable truth here: diesel will only work for you if you use your SUV in a particular way.
If, like a lot of modern urban-district dwellers, you plan to use your SUV as a family runabout with a majority of short journeys in stop-start traffic, then the diesel is probably not for you.
You’ll still get the fuel economy advantage, but servicing costs can creep up and the diesel engine simply doesn’t like this sort of treatment. It’s this type of use that causes modern diesels to gunk up internally and turn their soot filters into money pits.
If, however, you live in the country where every trip is a 50km deal, then a turbo-diesel car could be right for you, provided you can live with the rest of the package.
But an SUV to drop the kids at school and pick up the dry-cleaning? In 2019, it’s a high-tech turbocharged petrol every time, folks.