The decision on whether you buy a petrol car or diesel car is dependent on a number of factors and it’s not as simple as looking at the price per litre at the gas station.
Things to consider:
Diesel costs around 70c per litre less than petrol, however diesel comes with road user charges.
A tank of diesel will possibly get you 30% further distance, than a tank of petrol
Petrol is cleaner burning and has less CO2 emissions and in small vehicles is quite efficient.
The power output from a petrol engine is greater than a diesel engine however diesel produces more torque. High torque is important if you plan on towing anything, this is why you find most diesel engines are turbo charged, to make up for their lack in power.
As diesel burns less efficiently than petrol, you will be putting more pressure on the engine and over the long term you will require more maintenance than a petrol car.
If you travel small kilometers per year (15,000km or less) fuel saving on diesel don’t stack up when you pay road user charges.
Depreciation is a factor, a big SUV with a big petrol engine such as a 3.0L V6, although has high power also burns through the fuel, as such will depreciate faster than a smaller diesel engine as the fuel economy in the big petrol car is not great.
If you are planning on towing anything or driving lots of kilometers per year and like to have a big car; diesel is a good choice.
If you don’t drive excessive kilometers, want a small car and don’t tow anything, petrol is more suitable.