is it bad to use octaine booster more than two times?

[GT-S Celica]

i just bought five NOS octane boosters (increases 3 octane points) from my friend for $5.
the highest octane number i could fine around my neighborhood is 91 and i heard that celica needs 95 octane or something. so used it two times so far and some guy told me that useing octane booster is not good. Even though my car needs 95 octane. is this true? i would think it would do my car good.

[CBGTVA]

Unless you've done something to raise the compression, you only need 91 octane. Using anything higher doesn't do anything good for you and may even cause problems over time as higher octane fuels burn slower and may lead to carbon deposits.

As far as the 95 octane stuff, you may have seen that mentioned by owners in Europe. They measure octane differently and their 95 is the same as our 91.

[GT-S Celica]

ic, thnx for the info...
but isn't it true that celica needs more than 91 octane?
also, if your running lean due to a cai or something like that, and you get a CEL, will adding more octane help?

[CBGTVA]

Octane is only there to keep the fuel from predetonating or knocking and does not change the energy content of fuel. Unless you've done mods that affect compression, cylinder or head design, or the spark plug heat rating, the octane rating called for in the owners manual will do just fine. If you do mods like I've mentioned above and knocking does occur, the anti-knock sensor will pick it up and the ECU will adjust ignition timing to compensate and you may see a decrease in performance. In this case, adding octane would stop the knocking and allow the engine to run normally.

Adding octane to fuel will not change a lean condition. You have to add fuel or decrease air to get the air/fuel ration correct.

[RCKid]

Octane points do not go 91, 92, 93, 94, etc. They are decimals. 1 octane point is .1 added to the fuel. When you get that octane booster that guarantees 4-8 points increase, and you put it in your 92 octane gas, it is actually 92.4-92.8.