Pros and Cons - Diesel vs Petrol Engines In 2012

If a decade ago you were to tell someone that you drove a Diesel powered car the reaction you would get would be somewhat different to the reaction you would get today. Diesel has come a long way in terms of general motoring and diesel cars are becoming a pretty standard site on the roads. Although diesel cars have picked up in Australia over the last few years, they have been popular in Europe for many years before that.

Formerly the domain of trucks and heavy machinery, today there is a debate brewing as to which is better for the normal road car, Petrol or Diesel? This article is designed to give you the pros and cons of each and also explain a little about the differences between the two.

First let us explain how a petrol engine and a diesel engine differ. Both engines pretty much do the same thing, they convert the fuel (whether it be petrol or diesel) into energy through a combustion process forcing the movements of internal pistons which create a rotary motion through the crankshaft which drive the wheels. This is an abbreviated or simplistic description but it is sufficient for the purpose of this article. The main difference between the two engines is how the combustion actually happens.

In a petrol engine the petrol is mixed with air then compressed by the pistons and then ignited by the spark plug with releases a ‘spark’ which in turn ignites the fuel and forces the piston down.

A Diesel engine on the other hand the air is pre-compressed (as opposed to being compressed in the cylinder) and then the fuel is injected after that. Unlike the petrol engine there is no spark as when air is compressed it heats up and the fuel is then ignited that way.

In terms of which is better it comes down to various factors and at the end of the day and it is important to note that the driving experience is noticeably different between petrol and diesel. A few things to note:

Fuel Consumption and gases: Diesel engines are known to be more fuel efficient and generally require less fuel, often leading to about a 25% fuel efficiency. This in turn also means less greenhouse gases per drive. For example if you were to drive 100km with a diesel engine, you will burn less fuel and therefore emit less greenhouse gases than the petrol alternative. Saying that, diesel is a little more expensive per litre than standard unleaded fuels.

Costs: Petrol in its standard unleaded form is the cheaper fuel however diesel will travel longer on the same amount of fuel compared to that of a petrol powered car. To determine which one will be more cost effective you will need to factor in the mileage numbers for the car as well as the cost of petrol.

Health: Although emissions by both petrol and diesel cars are unhealthy, the Australian government has determined that the diesel pollutant is the more serious of the two.

Drivability: The drivability of the two is completely different. Diesel generally has a narrower power range and more torque down low with petrol engines generally having more top end power. This is a generalization though and we recommend you drive each version before your buy as your preference may differ from another.

Find your local Diesel engineer and specialist here on AussieWeb.com.au.

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