Not too many cars are designed to take advantage of premium. Actually, let me rephrase that - many cars on the market will not benefit from premium, only some will. Try it if you'd like, it won't hurt anything. Then try regular. Try the premium again. If you don't feel or hear a difference, save yourself the $$ and stick with regular!
is it something to do with the compression ratio of the engine?
here in australia is 10.6:1 and most of the cars I see with compression higher than 10 require unleaded petrol with 95 octane or higher. can anyone tell me is it a must to use premium petrol for any engine with higher compression ratio?
To confuse the issue my dealer in Wagga Wagga Australia said that the car runs fine on regular 91 octane and that they fill the cars on the lot up with it. I told him I'd have to see him fill the $45000 yellow one up with it to believe it. He seemed quite confident in the fact and said that with the car purchase a sheet would be added to the warranty, from Mazda Australia, to state that you could use regular in it. I got quite a different tune when I emailed Mazda Australia, but that might have been a standard response since they didn't answer either of my yes/no questions properly
I've done alot of research into this and can find no clear answer.
I'm gonna ask him for a copy of the before mentioned documentation and I'll let people know.
On my Miata, Mazda recomends US 91 octane (Premium) for best performance. But you can use a lower octane. The ECU will pick up the knock from the Knock Sensor and back off on the timing advance untill there is little to no knock. Car doesn't knock but performance suffers.
Bumping up the timing by modifying the Crank angle sensor is a standard performance mod on the Miata. Will be looking into this for my 6.
My understanding is that the North American Mazda6 is rated for standard, Regular 87 Octane fuel.
I'm certainly not the ultimate expert, but Consumer Reports notes in their "Car Care Myths",
"Myth: If regular-grade fuel is good, premium must be better.
Reality: Most vehicles are designed to run just fine on regular-grade (87 octane) fuel. A higher octane number doesn't mean that your vehicle will perform better. It simply means that it's more resistant to engine knocking or pinging. Use the octane grade that's recommended in your vehicle's owner's manual. Filling up with a higher grade is usually a waste of money."
I'm inclined to agree with what they say: If the manufacturer says regular fuel is fine, I'd stick with it and save money! Unless you're noting major predetonation problems, you might as well stick with 87.
Also, point of information: My understanding is that, indeed, higher Octane fuel doesn't necessarily mean better performing fuel; as in, it doesn't contain more energy than regular. Octane, from my understanding, is simply an agent that actually *lessens* fuel's explosive characteristics. Part of the problem with engine knocking and pinging is the fuel igniting before the spark plug goes off (compression ignition rather than spark ignition). Higher Octane fuel simply allows the engine to use higher compression ratios (because the Octane suppresses compression caused pre-ignition); thus increasing power per stroke. Higher compression means you squeeze in more air and fuel, so, with Premium petrol, the ignition stroke yields more power than regular fuel would safely allow.
Anyway, I digress! I was glad to see that the Mazda 6i engine is okay with regular fuel. Premium, when you add it up, is *a lot* more expensive than regular, and I'd much rather put the money saved on regular towards other car improvements!