The manual says 91+ so i usually put whatevers available.

 

Yeah, 91 or 93 doesn't really matter. If my memory serves me correctly, the purpose of higher octane level gases, aside from the fact that the factory engines are tuned with this level of octane in mind, is to prevent engine ping. Every notice more chatter or pinging in from your engine when you use 87 octane? Knock sensors are retarding combustion to deal with the lower octane level. Octane levels above 91 promote advanced timing...in theory? Don't quote me on this though...

Can anyone chime in?

 

I just stay with 76 gas station wit 91. cheapest and closest gas station to my home. one day, i accidently filled wit 87 n i felt different from 91. i felt 87 little bit slower n quicker ran out of gas.

 

I prefer to only use Shell V-Power but i every now and then i'll use a different brand so that my car doesn't get used just one type of gas. I will NOT use BP gas though.

 

wat is different 76 gas station n shell wit 91 gas??

 

Exxon Mobil 93 here in MD. I loved Sunoco 93 up in NY, but they dont have those stations around here. As for octane rules, you should put the closest to what the manufacturer recommends for best performance, anything beyond their recommended octane level isn't going to buy you too much unless the car is specifically tuned to take advantage of it. I can't get 91 here in MD, so 93 it is.

The higher the octane means more knock/detonation resistance in high performance applications (high compression), it does not necessarily mean more power. 87 octane will actually produce more power (burns faster/hotter) than 93 octane (burns slower/cooler) in an application designed to use it. Thats why putting in higher octane fuel like 91 or 93 in a car that requires 87 isn't yielding any additional performance, you may even be giving up some efficiency. This is why the manufacturer always recommends and tunes engines according to the octane they require. You always need to blend detonation resistance with BTU output for maximum efficiency.

 

Adam West pretty much nailed it. Lower octanes will burn hotter than the engine is designed for. Do our cars ping like older cars with lower octane?? Not really. Reason being is that we have variable valve VQ motors and our computers are constantly compensating.

Just because you don't hear a ping doesn't necessarily mean everything is alright. In the short term you might only notice the fuel mileage change. But the long term stress on the engine is not good and for this reason you should burn the recommended octane, or as close as you can.

Like some of the other posters I find the best fuel mileage using Shell V-Power. I am disappointed with fuel stations promoting the use of "cleaner" higher octane fuels for their customers. Only about 5% of cars are designed/tuned to run on high octane premium gas. Most cars have no benefit, maybe even lose efficiency running something higher than they are designed for. Sigh.

 

If you are using 87 and your engine is pinging, you could be doing mucho damage to your vehicle. It is no laughing matter.

ping definition:
And then the effects of abnormal combustion:

source: Engine knocking - Wikipedia, the free encyclopedia

I've always used 93 from Sam's club, but I think I'll go down to 91. I had a tune that required 93 for a while, but it is gone now, so why waste the money, I guess.

 

would higher octane...say 97 yield more HP or just a waste of money?

 

The stock ECU works at peak performance at around 91 octane.

The car will run on lower grades but treats it like any cheap, crappy gas you decide to dump in it: it pulls timing from the upper ranges (5,300ish RPMs in this engine) to prevent detonation. The highly adaptable ECU's in modern cars are what allow oil companies to sell us on this 91 crap in the first place.

Anything over ~94 octane is probably a waste, since, at least as far I've seen documented, the ECU isn't optimized for it.

Now, if you're talking to EVO/STi guys... you sure as hell can tell the difference between 91 and 93. I should know, I used to own one.

 

I live in Miami and the only octane levels available are 87, 89, and 93. I've used only Chevron 93 since i bought the car. Since you guys are saying u get better gas mileage on Shell v power im going to give them a shot. I would NEVER use any gas other than 93... but i have put 87 in a loaner before. Did seem to have a rough idle afterwards.

 

my g only uses 93 here in new york.

 

I always put 93 in my cars, but when I bought my G last week, the dealer said that the reason oil changes are more expensive at the dealer is because they use a special synthetic blend oil that makes it that you can run the car on 87 octane without issue.

 

wow ... total nonsense

 

i only use 91 and that's the highest octane besides 100 here in SoCal.