Hey jus wondering can we add a Octane Booster to our cars without any issues? The highest rating for gas in my area is 91. The Ralliart manual, claims the BEST persofmance is with 93. You can use 91, but with less performance. So if I add a octane booster additive for each fill up do you think it would cause any harm?

Thanks!

I've never heard of octain booster causing any harm, invreasing the RON number of a fule is always good because it means the engine's less likely to knock at high revs or under high boost. The only time i've heard of it causing a problems is when somone's used it to stop there engine from knocking when they turn up the boost, and then they turn up the boost to much and BANG.

I would say using 91 is probably worse for your engine as you're more likly to get a knock (detonation) when you put your foot down, it's supposed to sound like a ping in the engine, like metal hiting metal, but not having ever heard one i cant be sure. I wouldnt worry too much if you dont drive it too hard and dont hear any funny noises from the engine, manufacturers set these guide lines so that they can void your warenty when the engine blows up and they find substandard fule in your tank. Very few petrol companies can guarentee that all there fule is consistantly pure and of the stated octain value.

Living in the UK i know that the texico fule we use is the same 91 ron stuff from the states but it has bosster put into it to take it up the the 95 ron standard over here. However i've stoped using texico after i got a bad batch of fule which killed my engine.

honestly...you'll just be wasting your money. Octane booster is a scam. It says it raises your octane like 5 points or something like that, but if you read the back of the bottle a "point" is a tenth of an octane...so in reality youll be going from 91 to 91.5. Not worth the additional cost.
Your ECU will learn what octane you use and adjust the timing slightly to prevent knock. True, it will slightly reduce performance, but unless your comparing dyno slips you probably wont ever notice it.
but no, it shouldn't hurn anything.

ya i believe your right. I tried 1 bottle of STP and cant really tell much difference. So thats the last bottle lol. Thanks for the advice.

NEVER put any sort of additive to your car. This includes:

Octane booster
smoke stopper
injector cleaner
ET Cetra

Just wondering, whats the reason? Will it actually harm your engine?

It doesn't have any effect, and is just some sort of oil and then runs through your engine, possible doing the exact opposite of what it is susposed to do or more likely not doing anything.