Petrol Vs Diesel

Have you ever considered buying a diesel? Maybe you should.

There’s been meteoric growth in diesel vehicle sales right across the Australian market. In cars, diesel sales almost tripled from 2006 to 2012. Sales of petrol-powered cars actually shrunk in that same time.

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A lot more Australians are buying diesels these days, so let’s find out if one of them should be you.

There are plenty of advantages to diesel – and the first one is undoubtedly performance. Advances in diesel engines over the past 15 years have ramped up the performance without increasing fuel consumption. Modern diesel engines rock, thanks to high-pressure direct injection and electronic control. It’s such a plus that petrol engines are even copying it.

Diesels have higher compression so the burning mixture expands through a greater range in every combustion stroke. That’s fundamentally why diesels are more fuel efficient. You’ll drive every tank of fuel about 30 per cent further on a diesel.

So – better technology, and better thermodynamics. It’s why diesel often drives better.

Diesels make more power than equivalent petrol engines at about 2000rpm – which is why they feel like they go so much better in real-world driving conditions. Some so-called ‘experts’ call it torque. It’s actually low-rpm power.

Another big diesel advantage is range. Diesels deliver about 30 per cent better efficiency, which means you get around 30 per cent more driving out of every tank, which means less time stopped at the servo declining the latest two-for-one Kit-Kat proposal. You’re probably not going to miss that.

Plenty of modern diesels get more than 1000 kilometres out of every tank. That’s about three weeks’ average driving these days.

There’s also a reduction of about 30 per cent in greenhouse emissions. That’s between one and two tonnes of CO2 per annum, on average.

On the downside, refuelling a diesel just isn’t as convenient. There are about eight times as many petrol pumps at your average servo than diesel pumps, and sometimes finding the lone diesel pump is real ‘needle-in-haystack’ stuff. It’s a reflection of supply and demand.

Diesel pumps are generally leaky and dirty – so you often come away reeking of eau de diesel.

Car makers charge more for diesel engines – generally about $2500-$3000 more. You need to know that, if you buy a diesel, it will generally trade in for more than the equivalent petrol model. For example, let’s say a petrol car costs $40,000 and after five years’ ownership its value is now $20,000 (ie half what you paid). The equivalent diesel-powered car might have cost $43,000, but in five years’ time (all other things being equal) it will be worth $21,500. That is, the owner re-coups some of the additional up-front cost.

Diesels also cost a little more to service, because there are more filters and generally more (higher quality) oil to replace.

Another potential diesel disadvantage for urban-based diesel vehicle owners is the exhaust particle filter, AKA a catalysing particulate filter. This device traps microscopic carcinogenic particles in the exhaust gas, and burns them to less harmful smithereens, thereby preventing humans from breathing them, and getting lung diseases prematurely.

These particle filters never need replacement. But the car needs a run about every fortnight on the highway for the filter to burn off any trapped microscopic nasties.

If you don’t do that, the filter might not get hot enough to do its thing. If it clogs up, the engine defaults to ‘limp home’ mode (which is exactly what it sounds like). An unpleasant experience halfway over the Harbour Bridge, when you’re already late for work. When that happens you need to go to the dealership and have them manually regenerate the filter up on a hoist, which is uplifting … but only for the vehicle. That’s probably the worst thing about diesel vehicle ownership, potentially.