We get asked this one a lot at the pump: should you run 95 or 98 in your bike, or is regular 91 fine? The honest answer is that for most stock motorcycles, higher octane doesn't mean more power — it's about what your specific engine needs to avoid knocking, not a free performance upgrade.
What the numbers actually mean
In Australia, fuel is rated using RON (Research Octane Number) — 91 for regular unleaded, 95 and 98 for premium unleaded, and E10 sitting around 94 RON depending on the blend. The octane rating measures how resistant the fuel is to knocking (uncontrolled early ignition inside the cylinder) under pressure — it has nothing to do with cleaning power, energy content, or how "premium" the fuel feels.
Does higher octane mean more power?
Not on its own. If your bike is a stock, standard-compression engine designed to run on 91 or 95, filling it with 98 won't add horsepower, improve fuel economy, or clean your engine any better. The extra octane only matters once the engine actually needs it — otherwise you're just paying more for the same result.
| Fuel grade | Typically suits | Notes |
|---|---|---|
| 91 (Regular ULP) | Most commuters, naked bikes, lower-compression engines | Cheapest option — fine if it's what the manufacturer specifies |
| 95 (Premium ULP) | Most modern mid-to-high performance road bikes | Minimum recommended for many sportsbikes and higher-compression models |
| 98 (Premium ULP) | High-compression, turbo/supercharged, tuned or race-spec bikes | Only worth paying extra for if your engine actually calls for it |
| E10 | Modern bikes with fuel-injected, sealed fuel systems only | Check your manual — avoid in older carbureted bikes with rubber components |
When higher octane actually matters
Higher compression ratios, forced induction (turbo or supercharged setups), and aftermarket tuning or ECU remaps all raise the risk of knock under load — that's when premium fuel earns its keep. Older engines that have started pinging or knocking under acceleration can also sometimes benefit from stepping up a grade. If your owner's manual specifies 95 or 98, stick to it: running a lower grade than the manufacturer requires can cause detonation and, over time, real engine damage.
What we actually see in the workshop
In practice it's not quite as black and white as "use what the manual says and nothing else." A few things we see regularly on bikes that come through Kelmscott:
- 98 in a bike tuned for 95 can make cold starts harder. Higher octane fuel burns slightly slower, so in a bike that isn't tuned to take advantage of it, running 98 when the manufacturer specifies 95 can mean a harder start and slightly flatter performance in cooler weather.
- Australian summer heat changes the equation. Some bikes speced for 95 can start to knock or ping in our hot summer conditions, especially under load or in traffic. In that situation, stepping up to 98 is often the better, safer choice — even though the manual says 95 is fine.
- Properly tuned bikes genuinely gain from 98. If your bike has had its ignition and fuel maps optimised for higher octane — through a proper tune, not just filling up with premium — 98 can deliver a real power gain, not just a placebo.
The short version: the "check your manual" rule is the right starting point, but weather, how your bike is actually tuned, and how it behaves under load all matter too. If you're not sure which way to go, tell us your make, model and how it's been running and we'll give you a straight answer.
What about E10?
E10 (10% ethanol blend) is cheaper and fine for most modern, fuel-injected motorcycles — but check your manual before using it. Ethanol can degrade older rubber fuel lines, seals and carburettor components over time, so we'd steer older or carbureted bikes away from it even if the octane rating looks adequate on paper.
Booking a check in Kelmscott
If you're not sure what your bike is speccd for, or it's started knocking or pinging under load, bring it in and we'll check it properly rather than you guessing at the pump.
Not sure what fuel your bike needs?
Give us a call with your bike's make and model and we'll tell you straight what grade it actually needs.