What petrol is right for you?

03rd June 2019

Petrol is, at times, can extremely confusing. Each fuel retailing group has its brand names for the fuels it sells. And the petrol itself is available in four different types generally: 91, 95, 98 and E10. Sometimes it is tricky to understand which one to re-fill your tank with. This blog will go into what types of petrol are available and which ones you should use.

Types of Petrol:

Standard unleaded petrol is 91
Premium unleaded is 95 and 98
The ethanol-blended E10 (a mixture of up to 10% ethanol in petrol)

Those numbers – 91, 95 and 98 – are the ‘octane rating’ of the fuel. They’re all about the same in terms of the energy in the fuel. What octane is, is an index of a fuel’s resistance to burning too early inside your engine – if that happens, it causes ‘pinking’ which is mechanically destructive at high revs and large throttle openings.

Carmakers design engines for a minimum octane rating. If you open the fuel flap of your car and it says ‘unleaded petrol only’ it means 91 octane fuel is OK. If the fuel flap says ‘premium unleaded only’, it means you need to use at least 95. If the fuel flap tells you to use 98, that’s what you need to do.

Can You Use A Higher Octane Fuel Than Recommended?

It can’t damage your engine if you use a higher octane fuel. So, for example, if you use 95 or 98 in an engine designed for 91, that’s OK. However, it’s not acceptable to put in a lower octane fuel than the minimum recommended by the manufacturer. Using 91 in an engine designed for 95 or 98 can potentially be harmful to your precious car.

Fuel retailers love to talk up the benefits of their superior fuels. They don’t lie on this, but they do exaggerate the benefits. But in practice, the improvement is tiny if you choose a higher quality fuel and the price premium of the higher octane fuel always eclipses the economy benefit from running it – in other words, it’s not an economically rational choice to run 98 in an engine designed for 91, even though it might run only slightly better.

What About Ethanol (E10)?

It is essential that you note that E10 is not a replacement for premium unleaded petrol. If your car requires 95 or 98, E10 is not a viable fuel for it. However, the overwhelming majority of cars on Australian roads designed for 91 petrol can accept E10. Ethanol is an octane booster for petrol, so E10 generally has an octane rating higher than 91. This means your car will perform slightly better on E10 – but there is a downside. There is about 30% less energy in ethanol, compared with petrol. When it’s blended 10% with petrol, there is about three per cent less energy in the blend, and that means your fuel consumption will increase by about three per cent when you run E10 compared with 91 octane unleaded if all other things remain equal. Therefore, E10 can only be an economically sound choice if it is 3% cheaper than 91 octane fuel

Hopefully this post has provided some clarity about the confusing world of petrol and which option is best for you and your car. For more advice and information get in touch with ShreejiAutomotives today!