Car Advice

Should I choose a petrol or diesel car?

11 Sep 2017

Isaac Bober 3

Choosing between a petrol or diesel car is one of the first things a new car buyer should figure out before exploring spec, or even the type of vehicle they want to buy.

Petrol or Diesel? Not that long ago that would have been a rhetorical question with the answer being, well, unless you were a farmer, petrol. Yep, even as little as 10 years ago the default choice for all new cars was petrol, at least it was here in Australia.

But with improvements in technology and manufacturers sending a lot more of their diesel variants Down Under, thanks to our diesel finally being on par with the smelly stuff in Europe, the question of what type of fuel you should choose is becoming harder. And a lot more complicated.

See, with the arrival of clever diesel engined models into Australia mainstream motorists began to discover what 4WD owners had known for a long time, that if you wanted efficiency and grunt you went for a diesel. Simple. These new, cleaner diesels didn’t smoke like the diesel vehicles of old, they weren’t rattly or coarse at idle, and petrol stations around the country began putting diesel pumps onto the main forecourt.

Diesel cars began to grow in popularity, but in recent years the technology for both diesel and petrol engines has become even more sophisticated and so the issue of whether you buy a petrol or diesel isn’t so clear cut as it might have been. Indeed, the argument that diesel cars are more efficient and that petrol cars are more fun to drive isn’t always true.

When it comes down to it, though, there are really only three key factors you need to consider when choosing between petrol and diesel. And these are: Economy; Running Costs; and Your Gut.

Economy: Not so long ago diesel prices were at a premium when compared with petrol but, at the time of writing, diesel is cheaper than petrol. Choosing based on the dollars and cents of a tank of fuel right now would, however, be a waste of time as the price will no doubt swing back depending on taxes and production.

While many car makers make a big deal of their diesel model’s low fuel consumption it’s worth bearing in mind that those figures are recorded in a laboratory and not in the real world. That said, you can, however, accurately compare a petrol and a diesel car together on fuel consumption as long as you understand that it’s unlikely you’ll achieve the same figure listed in the brochure. See, your fuel consumption will be heavily influenced by where you live and what sort of driving you do: inner-city and only driving short distances; in the suburbs and stuck in stop-start traffic driving to work; or you might live in the country or just out of town and have a long, clear commute to and from work.

For instance, I purchased a diesel car because I live 100km from Sydney and knew that I’d be doing a fair bit of back and forth from the big smoke. Also, the in-laws live in Adelaide and we’d planned on driving to visit them at least once or twice a year. For my family a diesel car made sense, and on these longer drives regularly returns 5L/100km even when fully loaded (for the record it’s a Skoda Octavia 103TDI). On shorter journeys the ‘efficiency’ benefit of a diesel engine becomes less pronounced, indeed, in many cases it will be on par or maybe even slightly behind a similar model with a petrol engine.

The other thing to consider, although it doesn’t really fall under economy, but while a diesel-powered car might be, say, potentially 10-15% more fuel efficient than its petrol-powered sibling (the US Department of Transport claims 30-35% more effiicient, hmmm) it might also work out more expensive to own over a few years due to servicing costs being slightly higher for diesel vehicles.

Running Costs: When choosing between a petrol- and diesel-powered vehicle you’ll notice the price will generally be higher for a diesel model, although that premium generally reduces the bigger and more expensive the vehicles are that are being compared. So, if the diesel car you’re looking at is, say, $2000 more than its petrol-powered equivalent you’ve got to weigh up whether you’ll recoup that ‘premium’ in fuel saved over the life of the vehicle in your possession… if you don’t think you will, then you’re best off going for the petrol. In short, the shorter the distances you travel the less likely a diesel is to be of any benefit to you, the longer the distances you drive then the likelihood of recouping your ‘premium’ is greater. Do you follow?

More than that, the diesel particulate filter can become clogged if you only ever drive short distances without ever ‘stretching your cars legs’ on a longer, semi-regular highway run. The other consideration is that diesel cars tend to hold their value a little better than their petrol equivalent, so, while you might spend less on your petrol car, you might make less come resale.

Your Gut: If you think diesel cars are big, smelly, smoke-belching brutes then it’s time to think again. Improvements in engine technology and the fact diesels are more popular than petrol models in Europe which means that manufacturers are focussing plenty of their development budgets on diesels means they’re clean, quiet and gruntier than their petrol equivalent.

That said, while good diesel engines are generally more efficient (over distance) the line between petrol and diesel is being blurred as companies start producing diesel engines with petrol-esque response and petrol engines with diesel-esque lowdown grunt and fuel consumption. In general, though, diesel engines tend to produce more torque (the shove to get you going) than their petrol equivalent and produce that peak torque earlier in the rev range too making them feel, depending on the vehicle of course, a lot quicker than their petrol-powered sibling. And, modern automatic transmissions tend to get the very best from a diesel engine, meaning they can feel every bit as smooth and refined as a petrol engine.

For my family, where we live and the sort of mileage we put on our family car means a diesel-powered car makes perfect sense and saves us money at the bowser. Whether a diesel can do the same for you will depend on weighing up all the pros and cons.

This article was originally published in 2015 but is being republished because the topic is as relevant now as it was then.