WHAT IS THE PROPER FUEL TO USE IN MY CAR?

Petrol ratings can be confusing at the best of times. When you pull up at the fuel station there can be 4 even 5 options of fuel to put into your car. The numbers are what matters, standard unleaded petrol is 91, premium unleaded is 95 and 98 and then there are the ethanol blends of E10 and E85.

Those numbers are the ‘octane rating’. What octane is, is an index of a fuel’s resistance to burning too early inside your engine which can be destructive at high revs. Car manufacturers design engines for a minimum octane rating. This means it can’t hurt your engine if you use a higher octane fuel. For example if your car is recommended ‘unleaded only’ it means 91 octane fuel is OK. If your car says ‘premium unleaded only’ it means you use 95, or if it tells you 98 that’s what you would use.

So, using a higher octane petrol cannot damage your engine , if for example if it is recommended that you use 91 but you put in 95 that is OK. However it is important not to put in a lower octane fuel than recommended by your manufacturer. Putting in a lower octane fuel can be damaging to your engine.

Putting in a higher octane fuel can give you better economy or performance, but the amount of improvement is relatively minimal. The price of higher octane fuel isn’t economically rational given the minimal performance improvement you get from it.

Both E10 and E85 are ethanol based fuels. Ethanol is an alcohol made up of sugarcane, corn or other crops.

E10 is a slightly higher octane (94) than regular 91 in most cases, which means your engine performs better. However ethanol lowers the energy level of the blend by 30% which means you may experience a slight loss in fuel economy. Be sure to check whether your car is compatible with E10, if it is not, then using it can require a very expensive fix. Additionally E10 can rust out fuel tanks & fuel lines. It can also be harmful to the rubbers in the fuel system such as fuel hoses & injectors.

E85 has a higher octane level again, at 100 octane. For this reason it is commonly used as racing fuel. This is for its performance characteristics but, like E10, the energy density is lower than regular unleaded and fuel economy is potently hampered by up to 30%. Currently finding E85 can be difficult.

No matter which petrol your car needs it is important to use the right one, if you are unsure it is best to look at your car’s user manual.

If you think you have put the wrong fuel in your car or your car isn’t running efficiently send us an email or give BP Workshop a call on 3207 2224