E10 vs Unleaded 91: is it actually cheaper?

Published on 2026-09-22

E10 sits a few cents under Unleaded 91 on every board in the country. Whether that is a saving or an illusion depends on a number the sign does not show you.

Cheaper per litre, less energy per litre

E10 is 91-octane petrol with up to 10% ethanol. Ethanol carries less energy than petrol, so a tank of E10 takes you slightly less far — commonly cited at around 3% fewer kilometres, though it varies by engine and driving.

That means E10 needs to be roughly 3% cheaper just to break even. On a $1.80 litre, that is about 5 cents. A 2-cent discount is not a saving; a 7-cent one is.

Check whether your car can take it at all

Most petrol cars built for the Australian market since the mid-2000s are approved for E10, but not all, and some older vehicles and small engines should not run it. The owner's manual or the manufacturer's E10 compatibility list is the authority, not the servo.

If your car requires 95 or 98, E10 is not a cheaper alternative — it is a lower octane grade, and substituting it is a different decision entirely.

Where the real money is

Even at its best, the E10 decision is worth a few dollars a tank. The choice of servo, on a cycle day, is worth twenty.

Use E10 when the gap is genuinely wide and your car is approved for it — but do not let it distract you from the bigger lever.

Seeing both prices at once

Refil lists E10 and Unleaded 91 as separate rows for every station, with the cheapest highlighted, so the gap is visible rather than assumed.

That makes the break-even easy to judge on the spot: if E10 is not at least a few cents under, take the 91.

FAQ