91 Octane vs. 93 Octane
 

Need advice guys. I'm in Cali and our pump gas is 91. I found a place by my work that has 100 octane and I have a chart where I can mix 2-3 gallons of the 100 octane with about 9-10 of 91 octane and get 93 octane. There car will go to get tuned this week and I'm trying to find out if it would be better to tune for 93 octane.

Anyone in Cali doing this???

If you just have a few bolt-ons, it shouldn't hurt you to use 91. It very much depends on the blends of fuel and what mods you have.

Also, ask yourself what you want out of the tune. If you want every last HP you can get, and are OK with being tuned on the edge, go for the highest octane you need. If you're trying to drive the car regularly (aka not just at the track) then you're probably like the rest of us, and would be fine leaving a few HP on the table knowing you're a bit safer.

no, makes no sense,unless you have issues ie pinging, tune for the gas available,91- 93 not much difference anyway, Just buy from the biggest stations that sell the most and have the freshest, I would take fresh 91 vs stale 93 anytime.
How do you know that a station that sells 91 isn't better than 93
since these are minimun valves anyway.

I got a 427 in the car. I am going to be driving the car as it's a street car, not a track only car. It's got straight pipes right now and I'm going to be putting some high flow cats on it as it's too loud. I guess I want to make up the HP difference I'll lose by strapping some cats with a higher octane gas. :smash:

Makes sense...

I have heard a lot of good about "Top Tier" fuels....... use a 91 such fuel, then hey, find out for yourself, go to the dyno with 10+ (oh and 9-10 + 2-3 does not = 18......... fyi) gallons on 91 in it, get a tune, add the 100 to take it up that extra notch then see if the gains are worth the extra $15+ every tank full........ and heck, let us know! Keep in mind (I have done an excel of what you are talking about, and after every tank the "starting" Octane goes up........ till it reaches it highest point).

I would contact jbsblownc5 and get some Torco. One can of Torco mixed with 10 gallons of 91 will give you 96+ octane. More cost effective than mixing in 100 octane.

If you decide to do it, make sure your friends 100 octane is unleaded. For example Aviation Gas comes in high octane, but even the LL (low lead) has a bunch of lead in it...(it's only low lead compared to "high" lead AVIATION Gas)...

You probably already know, but just in case...

MD:cheers:

Yeah, there's a station in San Jose that has 100 octane unleaded racing fuel. It's street legal. In hot weather, I mix about 3 gallons in a tank up. The car seems to run a little better with it.

When there's a gas pinch on, like this summer, the super seems to be crappy and I'm guessing it is just the barely legal definition of 91 octane.

Like someone else mentioned, do not even think about running avgas 100LL. It has more lead in it than any highway fuel ever did. It is nasty stuff and fouls plugs, sludges oil, and of course kills the catalytic converters.

NOS Has a fuel adder that claims to boost octaine by about 7-10 points, I don't know how good It Is but If It works It would save some$$

Why so much hassle to just get 93. Are you always going to be carrying this mixture in your car? You just want to do this to get more HP from the tune correct? Why not just buy some power adder and get that extra HP that you want and be able to use 91 octane all the time and be able to purcahse fuel anywhere in the US.

So you this this mixture...get 93 octane...then you have to put some fuel right away at 91....that changes the mix...now you put your mix...is that 93 still?

YOu just get a tune at 91....a little hp is not felt at all. IF you track it, practice is going to get you better times not HP.

Good luck.