Premium or regular unleaded?
 

What do you use? I've been using 91 octane premium for whatever more power I can get from it..

using 91 doesnt give u anything, if anything it takes away, unless ur car had advanced timing so it would need a higher octane

-Yep. If you have a stock motor, and don't get any pinging or knocking when you use 87 octane, then you're just flushing your money away a little bit more at a time.

L8R,
Matt

i have been running 93 octane in mine since building my head, runs alot better, it dont like the 87 anymore. runs like **** with that in it.

I honestly feel like 91 adds more power. Its not much but anything is better than nothing

No gasoline adds power, period, just to point out.

Higher octane can give a 'sense' of increase in power, though its only more spark advance(not actually horsepower gains) to give the sensation of 'more power'. IF your car has problems running a lower grade of gas you may be on the verge of having knocking/pinging set in. It should be able to run lower octane just fine, but if you treat your gas, say once every oil change, with something like seafoam and lucas, then you'll perhaps be able to offset any performance loss that comes from running lower octane constantly and having 'dirtier' fuel all the time, but you can get bad gas with any octane, right? So, a good regimen of gas treatment, the ones that actually work, every so often and you'll be fine with running regular 87 instead of any grade of premium on these cars.

Explain why dyno runs prove that (in other cars) race gas like 95 octane adds lots o power.. I'm not saying I'm even getting 2hp out of it but statistically it should be adding some.

Some cars, like flex fuel cars that want to use E85, have 1 of 2 scenarios. Some flex fluel cars have the PARTS to be able to run E85 and not suffer potential degradation and subsequent failure of fuel pump etc like our cars(neon stratus etc). One thing to mention is that if the flex fuel car can run E85 doesn't mean it can compress, at least not without the right kind of programmer with it or ignition control module like in turbo applications, to see any benefits in gas mileage.

Example:
My friends Titan is a flex fuel but it doesn't get better gas mileage with E85 because he had a power programmer set to run 93 octane to maximize performance gains and for that octane of gas and those type of programmers are 1 time deals so to speak. The problem with this set up is in order to see an equalizing or maximizing of potential by running this higher octane E85 something needs to happen. It needs to compress this higher octane of gas at a higher compression rate, because its e85 in particular. Air/fuel ratios etc as well. So, even if the vehicle can be labeled a 'flex fuel', basically if the car is compressing it as though it were your standard gas 87-93 octane, then while you may notice some benefits, like a cleaner fuel line, your computer is 'dumbing down' any potential for real gains because its not adjusted electronically to use this increased octane. So even he is limited because his power programmer doesn't know to compress differently for the e85 and the potential gains to be found with a higher octane isn't to be found like he could have if his programmer had an option to say he was running e85.

Some flex fuel cars ACTUALLY ARE flex fuel in the truest sense, because they will compress at the higher ratio and know that, yeah you have E85 in the tank and the mixture needs a higher compression ratio, thus giving you the added power sensation PLUS+ no loss in gas mileage(if you don't go WOT all the time of course. :) ...in America though the same cars overseas that have the computers in them to compress differently based on the octane, are dumbed down here.

The difference in the end is our cars would need to be able to compress at the higher ratio and to utilize a higher octane more efficiently, like these modded cars with all the gadgets and computer tweaks to get TRUE gains for the higher octane. In any case, without such power programmers our fuel systems inability to run E85 for examble, combined with the computers we have don't know to burn more efficiently an e85 gas anyway or any octane difference for that matter. What happens, though, is we do have the mechanical parts still working for us. So it will be a better burn with less chance for pinging and knocking so the sensation of more horsepower is just a better burn. You're not actually getting more horsepower at the wheels in our cars...but thats just IMO based on some research I've done. I'm probably not 100% accurate, but that can give you some direction as to cause/effect with our car versus the ones that can take advantage of octane boosters more so.

Because when they run that octane, the engine [computer] is tuned to give more power because the higher octane will keep detonation from happening. If I filled up my Mustang with 100 octane, it will not all of a sudden have a gain of 20 HP. I have my computer tuned to run with 91 octane vs 87 for some HP gain. I HAVE TO run 91 or higher octane with the tune or there will be trouble. The reason a car on 91 octane could make, say, 500HP, but on 100 octane, can make 700HP. Statistically, you are wasting money.