Ok, being the idiot I can be sometimes, I put in about 4 gallons of 89 gas into my car the other day. I then made sure I filled the rest up with 93, but is this something I need to be worried about? Is it possible I will run really lean? I have read that even one tank of gas can screw things up.

My car is basically a stock 94 with around 25,000 miles. Is there an additive I should add? Do I need to drive this tank out like an old lady? Or am I worrying over nothing?

Thanks in advance.

 

well if u put in some octain booster that should be enough to mix the whole tank so nothing can really happen...because if u only put 4gallons of 89 in a 17-20gallon tank, all u need is some concitrant to make it stronger

 

Most likely you shouldnt have to worry about it. But for some peace of mind, go to the hardware or paint store and buy a gallon of toluene or xylene. Add it to the tank and you will be fine. Octane booster is crap...

 

ooo i just learn something fo rmyself...what does that stuff do?

 

4 gallons of 89 mixed with 16 gallons of 93 is still going to have better octane than the 91 that I can over here in Cali.

 

like Peter said i wouldn't worry about it if you already topped up with 93 octane. if it was a highly modded engine i would maybe worry but you only lowered the octane by about 1 point with that mix so don't worry about it.

and as far as mixtures go, no, the octane of fuel has nothing to do with AFRs, it has to do with when the mixture is ignited which may affect AFRs ever so slightly but the main issue with octane differences is that the lower the octane the easier it can preignite under boost and higher temperatures as well it burns faster so with a more aggressive timing curve that performance engines have there is a much more likely chance of detonation with lower octane fuels as the timing is not matched to the burn rate of the lower octane.

 

well just keep away from boosting and racing around on that mixture, even though here in cali we get the crappy 91 we still have to tune it richer to compensate for the lower octane.

 

toluene and xylene are a paint thinner. They are also the main ingredients in those octane boosters that are of so low concentration. Toluene carries an octane rating of 114 and xylene i believe is like 117.

For a little bit of history, they used to run over a 70% mixture of toluene in the old indy cars that were running like 70 something pounds of boost on little 1.5 liter motors and creating 1500 hp. the stuff is definately proven, and i personally run it in my car on a regular basis.