PETROL may contain less energy than diesel but both contain a great deal more energy than ethanol, which offers a very poor energy return on a volume or weight basis. In fact, ethanol has one third less energy by volume than petrol, or put another way, petrol has 50 per cent more energy by volume than ethanol.
Ethanol makes up 10 per cent of E10 fuel, and ethanol’s lower energy content is the reason why your car won’t go as far on a litre of E10 as it will on a litre of straight petrol. E10’s lower energy level erodes its lower cost at the pump, sometimes making it more expensive in the long run.
What’s not to be confused here is that ethanol has a higher octane rating than petrol, which means it’s useful for engines running high compression ratios and/or forced induction such as turbocharging. In other words, it’s a good racing fuel when you’re not concerned about fuel economy.
If you’re a diesel driver who thinks none of this is a concern, you need to think again. We all pay for ethanol via a federal subsidy of around 38 cents per litre, which makes it cheaper for those people who buy it. Effectively we are all paying for ethanol, despite the fact that it’s an energy-deficient fuel of dubious environmental value. Go figure.