There's absolutely no harm in running 103.5 octane as long as it's unleaded (lots of high-octane race fuel is leaded...so be careful!). Gaving said that, there's no benefit to running 103.5 if your car is flashed for 93. Anything over 93/94 and you're just burning money.

What we're talking about in this thread is adding high-octane fuel/additives to low-octane gas for guys who live in places where they can't get anything over 91/92 octane. They're talking about mixing 91 octane pump gas with some race fuel or homebrew octane booster to raise total octane to the 93/94 range.

If you can get 94 at the pump where you live, then ignore this thread!

Emre

 

thanks for saving me the money

Ben

 

yes. absolutely safe .

i use toluene frequently, i think it's the safest octane boost you can use, besides just using race fuel.

people who say otherwise simply don't know what they're talking about. THESE guys DO know what they're talking about:

http://www.bp.com.au/products/fuelnews/faq.asp

the one thing that DOESN'T recommend is MMT, which is the main ingredient in many octane boost formulas. and guess what? the brands that don't use MMT use toluene or some other aromatic.

so does it make sense to pay ~$6 for a little 8oz bottle of boost , or buy toluene from sherwin williams for ~$7 a gallon?

now, that said, there a few basic guidelines i go by, personally:

1- i live in the land of crappy gas, california. i only boost my octane to what i consider a proper level, ~93-94. i'm not trying to mix up rocket fuel here. why?

-the stock ECU is generally considered to be unable to optimize for any higher octane. map your system for 100 octane, and this will change, obviously.
-the toluene mix required to get there is about 10-15% for us 91 users. well below BP's (and others) recommended max.
-i've experimented. adding one, two and three gallons at various times while driving hard. one gallon in a tank is a big improvement over street gas, two gallons is an incremental improvement over one, and three makes no noticable difference over two. one gallon= best bang for the buck.

2- i use race gas when it's convenient and cost effective, e.g. at the track, in a pump, for $6 a gallon. i use toluene as a substitute, but i'm not about to claim it's better than the real thing.

3- i mix ratios by volume, not by fill-up. as with two-stroke engines or any other application that requires a stable mix, you can't "add one gallon and fill it up", or the mix will get stronger with every fill-up due to the leftover mix in your tank. the proper way to mix is, for example, one gallon toluene to 11 gas, or 2 tol to 10 gas, or whatever, and don't worry about filling your whole tank. keeping the ratio the same is as easy as keeping the two volumes the same every time. people who argue this point are just thick. it's pretty simple stuff.

4- i don't add anything else. ATF, marvel mystery oil, nothing. waste of time, in my opinion. at the fairly weak ratios needed to get a couple full points of boost, it's just not needed, and adds hassle and handling, which you really should minimize- this stuff is pretty nasty. i'd be more concerned about adding too much ATF to my gas than adding straight toluene, honestly. how much ATF is too much? no idea, just the guesses of a bunch of dudes on a web site. how much toluene? well, what does BP oil say?

http://www.bp.com.au/products/fuelnews/faq.asp

...THAT, to me, is the definitive word.

 

oh, and about xylene, the same theory applies, i think.

eating rubber? ruining cats? adding lube? oil catch can?

egad.

what does BP say?

http://www.bp.com.au/products/fuelnews/faq.asp

...ah, right. they don't mention the xylene. makes it pretty easy, don't it?

just my $.02