As mechanics, we regularly hear our customers are confused about premium fuel. Their car might specify they have to use it, or recommend they use it. There’s a lot of conflicting opinions out there about premium fuel, what it does, and whether or not you need it. The truth is, premium fuel does have some benefits and some cars may need it. So, should you use premium fuel in your car? Much like humans, there’s not a one-size-fits-all diet for cars — it’s a bit more complex than yes or no.
What even is it? It normally has a flashy name like Premium, Super Unleaded, or Ultimate Performance… but what is it? In Australia, our current fuel standard is 91 RON (Research Octane Number) — this is the fuel most cars accept and the one that has the long lines at the servo. Increasingly though, there are cars that need 95 RON premium fuel and some even fancier cars in need of a 98 RON premium fuel. Premium fuels are normally around 12 cents or 10% more expensive than regular kinds.
So, the difference between the fuels is all in the octane level. Octane determines how much compression the fuel can take before igniting. This means a premium fuel will have more octane so it won’t explode or pre-ignite as quickly as its cheaper counterparts. This is where premium fuels becomes more valuable in high performance or luxury cars. These cars’ engines will have higher compression rates than your regular family car. Cars that specify you need to fill them with a premium fuel or a fuel with a higher octane level should typically have a high compression engine and typically work more efficiently and emit less emissions.
If you have a car with a high compression rate and you choose a lower octane fuel or a regular kind you may experience ‘knock on’. Knock on happens when a car with a high compression ratio uses a normal fuel. Normal fuel will ignite prematurely due to the space inside the cylinder. This causes knock on which is just a knocking or rattling sound inside your engine.
Knock on isn’t necessarily bad for you car but it’s not ideal and a heavy knock can actually result in damage to your engine.
Not really. If your car needs premium fuel then using a normal kind can decrease your car’s performance. If your car doesn’t need premium fuel, it won’t have much of a benefit. Your car’s horsepower is its horsepower and fuel can’t change or affect that. The only difference it could make is better economy. However, the savings in increasing your fuel economy with premium fuel will be so slight, they won’t outweigh the extra spend.
Check your car’s fuel door (there may be a sticker there) or double check your car manual. If it specifies your car needs to take a premium fuel, then use one. If it recommends you use it, you don’t necessarily need to — but in some cases, using a fuel with a lower octane than your car recommends can be damaging.
This is usually the cheapest fuel option. It’s not necessarily compatible for every vehicle but it’s safe for most modern cars. The fuel economy on this one isn’t ideal and the fuel is part ethanol (up to 10%).
You can find 91 pretty much everywhere and it’s what most cars run on. It’s more expensive than E10 but it’s the moderate choice for most cars. Though, a lot of modern car models will specify they need a higher octane level than 91.
Your 95 option is the mid range premium fuel. It’s good for small, high-performance cars and is a fair bit more expensive than 91. This one isn’t as popular as the 91 option.
This one is the ultimate performance fuel. It’s even more expensive than the 95 but is worth it if your car requires premium fuel. If you have a performance or luxury car, the 98 option will likely be for you. People argue this fuel can ‘clean’ injectors and engines but most fuel types include this special detergent too nowadays.