Octane Booster Fuel Additive

Likely the 104+ just contains a mix of toulene or xylene and other additves. But the real octane boost comes from the toulene/xylene. So you are paying alot for a bottle.

I have used up to 30% toulene (70% premium unleaded) with good results on a circle track engine running 11.8:1 comp ratio (flat top magnum 360 - 36deg timing). This is also at 2500' above seaevel: closer to sea level would require a slightly higher octane level. The rules stated "no race gas" so I followed the rules. If the rules would have said "no paint thinner" I would have been in trouble. Also the cost was about 1/2 of race fuel.

If you are using this on a street car to eliminate some pinging I would try blending in about 5% toulene and see if it fixes the problem and then go higher or lower as necessary. I would not waste my money on 104+ because you buy alot of toulene for the price of the 104+. (and the 104+ is a bit of false advertising, because to actually obtain 104+ octane you would need a whole lot of it). You can buy toulene by the 5 gal pail (I think I paid $80 for the pail).

As was mentioned the best (and most expensive) alternative is race gas.