Fuel Showdown: Diesel Versus Petrol

Image: iStock

And so we arrive at one of the most debated topics at present; diesel versus petrol. The efficiency of each, no matter your choice of vehicle, is a factor that can save you financially and also protect the environment. It's a small decision with the potential for big impact. Here's what you need to know.

Arguably, diesel has been the poster child of fuel economy for the last decade. But is that the whole story? If you’re a boat owner, then you might prefer a petrol engine which is low-maintenance and relatively quiet by comparison; much more appealing for a cruise around the bay.

We take a look at both options so you can work out which will be better for you in the long run.

What About Diesel?

Diesel is a fuel mixture of hydrocarbons obtained from petrol which ignites without spark due to air compression. In short, the point of difference is that diesel engines rely on compression in order to power the engine.

From this, diesel engines are larger in size and tend to be far more complex than a petrol design, allowing them to produce more torque. This is neither an outright positive or negative, it really does depend on your vehicle size. However, if you’re in the market for a small car, then you’re likely to find more choice in a petrol engine as a result.

As far as high-speed performance, here is a simple way to make the comparison. Petrol is flashy and works very well for short and fast trips. Diesel is a workhorse; slower, but able to endure for the long run. If you use your car less often, say, to drive to the station and back during the week, then a diesel engine isn’t a necessity.

Certainly, diesel engines tend to be more expensive upfront than their competition, but that doesn’t mean they can’t save you down the track. As a general rule, diesel uses less than 30% petrol, which can easily negate the initial cost and your ongoing petrol expenses.

What About Petrol?

A petrol engine is an internal combustion system that is ignited. The process differs from a diesel engine in that the fuel and air are usually pre-mixed and uses a spark ignition.

On the whole, petrol engines offer better day-to-day convenience. They tend to be smoother than diesel, require less maintenance and, at a petrol station, they often outnumber diesel pumps eight to one. This means there’s much more to choose from, which is great for your budget.

If you’re taking to the high seas, then petrol is a firm favourite of many boat owners. It is generally considered cheaper to run and low-impact. The biggest bonus of a petrol engine is the amount of noise and vibrations it doesn’t make, which is appealing if your boating is purely for leisure. Sailing the harbour and shoreline with a loud motor is a sure fast way to attract unwanted attention!

So Which One Is Right For You?

You have the major arguments, now you need to look at your situation and decide whether petrol or diesel is the right choice for you. Here are a few key factors to consider;

  • If you’re looking for a brand new vehicle, the diesel model may cost up to 15% extra compared to a similarly equipped petrol engine car.
  • What is your primary need? If you travel often and for long periods of time, perhaps for ‘road trip’ holidays or to visit family interstate, then diesel could be the better option.
  • How much maintenance are you willing to put up with? Though there are no guarantees, the complexity of the diesel engine can make it more difficult and costly to repair.
  • If you value your environmental conscience over cost and efficiency, then the signs point to petrol. A complete lack of progress in cleaning our air can come as no surprise when over half of all new cars are now diesel.

At the end of the day, it really is all a matter of perspective and understanding. Recognise the drawbacks of your options and evaluate your usage before making a decision. Ultimately, remember that the world of fuel is constantly evolving in line with sustainability values and high-tech advancements. So though you might make a choice today, it’s never too late to change your mind tomorrow.

Samantha Pudney loves all things engine! Her position at Power Equipment means that she has a front of the line view of industrial engines every day.


    Good Dog! Here are a few corrections:

    Motor boat owners generally prefer petrol engines but yachts pretty much exclusively use diesel engines. And, yes, yacht owners use their engines all the time, especially cruising yachties. That means if you are taking to the high seas, you'll probably want a diesel, not petrol.

    Diesel engines are not necessarily more complex than petrol engines, its' just that because they are so popular in Europe, they have had a lot of extra development in the last 20 years. But a modern turbo-charged, direct-injection petrol engine is as complex as a modern diesel.

    Because of the above, a modern turbo DI petrol engine is almost as economical as a diesel engine anyway.

    Diesel engines are dirtier and far worse for your health. Europe's strict regulations of diesel particle emissions is what prompted VW to cheat. One of the big expenses diesel owners have that petrol owners don't is replacing the particulate filter. Many are supposed to be self-cleaning but unless you flog your car, which most diesel owners don't, it ends up clogged and in need of replacement. It uses Platinum so expect replacement to cost two or three grand.

    Nowhere near half of all cars sold in Australia are diesel. Last time I saw any figures, diesel accounted for around 15% of the total number of cars on the road and were less popular with new car buyers than they were five years ago.

    If you want to save money and help the environment, convert your car to LPG. It emits less 40% greenhouse gas and is half the price of petrol. You will use 15% - 20% more LPG than you would petrol but overall you will still be well ahead.

      I thought it was California's strict emissions requirements that led to the VW execs selling out the Earth's future for profit. At least they weren't in the business of selling tobacco or fossil fuels, or of extracting minerals or exploiting living resources like forests or fisheries, because if any corporate types from those industries put short-term profits ahead of longer-term considerations we'd really be f%#&@d! You raised some excellent points that probably should have been in the original article, especially regarding LPG. It would've been useful to include hybrids and all-electric vehicles in the comparison as well, as car buyers can acquire these technologies today for a premium, and may even be deferring a purchase in the hope that established car makers follow Tesla's innovative lead and showrooms begin to fill up with all-electric offerings in more shapes, sizes and price-points.

      Yep, I was surprised to see no mention of how dirty diesel is compared to petrol, which is a big deal these days. Just thought I'd mention though, gas is cheaper to run, but it doesn't lubricate like the other fuels, which causes a few problems if you aren't prepared for it.

    A few more clarifications to add to the above,

    Diesel engines aren't more complex than petrol ones. In fact, it would be easy to argue the opposite since they don't have high-voltage ignition systems or spark plugs.

    The greater torque is derived from the high compression ratio and more efficient burn in diesel vs petrol engines. This naturally allows them to be turbocharged without modification (unlike petrol engines) yielding even greater torque. The higher torque generation permits lower revs which generally reduces maintenance requirements.

    While diesel is more fuel efficient, it's not necessarily cheaper in the long run. Mainly since the government applies a higher excise to diesel knowing that drivers buy less of it.

Join the discussion!

Trending Stories Right Now