What Fuel Should I Use in My Car?
Non-car enthusiasts are very confused by this question. And the fuel companies haven’t helped – the number of different retail fuel products beggars belief.
In the past few years we’ve seen an explosion in the number of fuel products – many of which bear absolutely no resemblance to the way fuel is actually specified by car manufacturers.
Automotive fuels currently on offer include:
Standard unleaded petrol (ULP), which has an octane rating of 91 and is being phased out in some states, soon to be replaced by E10. It’s the fuel most petrol cars on sale in Australia require. (It’s the one that goes with the ‘Unleaded Fuel Only’ sticker inside the fuel filler flap.)
If you’ve been using 91 ULP and it’s become unavailable in your area, and your car is incompatible with E10, you’ll have to use the next fuel in our list, a premium unleaded petrol, which is more expensive. (interestingly, E10 can also damage mowers and other yard equipment in the manner described above. It's generally a safer bet to run these items on a premium unleaded fuel. (They consume very little, so the running cost difference is negligible.)
E10 will help a suitably compatible 91-octane-minimum engine perform a little better, too, allowing the engine to advance the timing a little, but it packs less energy into every litre, so your fuel consumption invariably goes up, offsetting most of E10’s upfront price discount. The performance increase will be very minor, and the consumption goes up 3-4 per cent.
Premium 98-octane unleaded (PULP). This is the fuel demanded by some exotic cars, often with forced induction (turbo or supercharger induction) or 'direct injection', and the most expensive petrol on the market. If the car says ’98-octane Unleaded Only’ you must not use any of the lesser petrols, because you could severely damage the engine, landing you with a bill an ordinary mortal might not jump over, given the nature of some of the cars that require 98.
E85, a blend of up to 85 per cent ethanol, with the balance in petrol. The recipe varies by place and season; it's not always 85 per cent ethanol. Currently this fuel is available only at some selected Caltex servos and is called ‘Bio e-Flex’. The only cars - so far - that can run it are the latest ‘Flex Fuel’ iterations of Holden’s Commodore. If you stick this green-oriented fuel in basically any other car, chances are you won’t get it started at the next cold start. Cue the expensive repair bill again.
Most engine design experts I’ve ever spoken to regard running higher octane fuel in an engine designed for a lower octane fuel as basically a waste of money.
One fuel manufacturer that has recently taken a real step in the right direction is Caltex, which has taken the decision recently to display the meaningful numbers – 91, 95, 98 – on every bowser. It's really useful information to help ordinary consumers cut through the branding to the essential information.