It's probably fine to run regular if you never run your car past 1/2 throttle. If the cars volumetric effeciency isn't very high there will be less cylinder pressure before ignition. Pressure and temperature are what cause detonation.

I still think it's a bad move, and would never recommend it.

 

given the rate at which our govt. is subsidizing ethanol and promoting it's use in gas as a replacement for MTBE that's going to just get harder.

 

I will never understand why people use less than 93. If that extra few dollars is going to break your bank...DON'T buy a car that runs on premium fuel!

 

I think that 91 is "premium". We can't get 93 here, but I think that's "super".

 

here in cali i'll take the most premium i can get.... lol

japan gets like 101/103octane premium, makes tuning turbo/sc cars out there so much easier...

 

here is a link to a good article explaining octane. a hydrocarbon unit is a carbon atom with one hydrogen atom to the top, and one to the bottom. the chains they refer to are hydrocarbon units connected side to side. if eight of them (the carbon atoms) are coinnected side to side that is an octane. the energy released does not depend on whether you are exploding octanes, heptanes, or any other "tanes. all gasoline has several different 'tanes in it. its just that the higher the octane, the more of the longer chains it has. this reduces volatility and means you can compress it more (which raises the temperature) before it self-detonates without a spark. it is the explosion in a smaller space that leads to greater power being supplied to the drivetrain, not the inherent qualities of the gasoline.

http://auto.howstuffworks.com/fuel-e...uestion901.htm

there was also a show on this that might have been in the "modern marvels" series, but i'm not sure of that.

at higher altitudes, the thin air effectively raises your octane rating by 2-3 points. i'm in denver. i burn regular (listed as 85 octane) and never have knocking even when driving up through the mountains up to 143,000 feet. both before and after the switch to regular i got right around 19.5 mpg overall. i live in the burbs and don't do a lot of true "city" stop and go driving.

 

certain 76 stations here in socal have 100 oct but at around $8/gal that's expensive.

91 oct for me all day, shell/chevron/76 only. we can debate about the quality of gas in another thread.

 

I use 89 all the time and it runs great. I should try the 87 but haven't yet. If you don't get preignition and see no loss of power you will be fine. Try 5 gallons the first time.

 

before i get any wisecracks, let me set the record straight. i haven't driven up to 143,000 feet. only 14,300 feet.

 

I live real close to one of the 100 Octane 76 gas stations. It is crazy expensive but, having 100 octane close by has helped me out in the past with a couple of my vehicles. Now, I simply use water injection to cure my need for expensive high octane fuel.

In my LS, I use 91 octane.

Mike

 

Using gas with ethanol in it should yield lower mileage since ethanol is "lighter" and you need to flow/burn more of it to get the same amount of energy as regular gasoline. It will also not do anything for octane rating, 87 with ethanol is still 87 octane. Gas cap says "premium only", 87 isn't so YMMV (I wouldn't even try it personally).

I use the best fuel I can which around here is 91 octane from Chevron. All of our fuel has 10% ethanol in it.

Stan

 

91 or 93 as well.

 

If the car's manual says premium i give the car premium, every other car gets 87 lucky in NY we have 93, if a car is stock there's no reason to use more than what's needed, it's funny when guys throw 93 octane in a civic and expect to hit anything faster than the usual 18's in a qtr

 

Using higher octane than tuned for is common for track days, engine should run cooler. Those Civics do have very high compression ratio, as do our cars.

Stan

 

common where? if your car is tuned for '87, running 91 is a sheer waste of money.

even people at track days don't wanna waste money