Here is the scoop the way I understand it (I could have been drinking heavily at the time...so don't take my word as the truth!).

First, the higher the octane the slower the fuel burns! Really! A lower octane fuel will actually ignite quicker - that is why you can get knocking on cars that do not have automatic timing adjustment - the fuel will ignite before top dead center (you get a knock as the piston forces its way up a little further before coming down). However, a quick burn does not mean as much power, as it does not take full advantage of the complete power stroke. Higher octane will prevent this pre-ignition. (like I said...this is how I remember it...there likely is someone much more technical than me that can FULLY explain this).

Putting a higher (numerically) octane in a car that does not require it is acutally a waste of money - if the car is designed to run on 87, it has been designed to draw the most power out of that fuel. If your owners manual says that you need higher (SSEi) for example, then you need to burn that fuel. I understand that in a pinch you could use lower octane fuel...but should return to premium as soon as you can.

All that being said though, I am told that some companies (ie. Petro Canada up here) actually put more cleaning solvents in their higher grade of fuels...therefore, you might want to put a higher grade in to get that benifit. Shell has TV ads running up here that say that if you use their premium fuel, you will actually get better fuel economy.

But it might just all be anyway! How do you know if you are really getting better fuel?

I guess you just need to decide for yourself. The biggest factor may just be your wallet!!

i run 94 or 105 race gas. i tend to get better gas mileage off of 94 than 93 but the price doesn't bother me

They sell this Blue Racing fuel here. Its 110 Octane. $3.90 a gallon.

Rob

That'* usually leaded in those octane levels. Be careful.

Definently dont want to be running racing fuel through cars that have O2 sesnsors on them. On our Accord web forum we had dyno sheets taht showed the different performance levels of each octane, & how much it hurtt perforamnce if you didnt run the recomended octane rating.

When I was getting out of the Navy I had to borrow my Mothers Izuzu Trooper to load up all my things. Well she had to drive my Tbird SuperCoupe. When she fueled it up she used 87 octane and the car never ran right afterwards. It took 4 tanks of gas and 4 bottles of octane booster to keep it from spark Knocking at 5 psi boost or more. After that I changed spark plugs and alot of them showed damage. The car never idled right again. I replaced a few sensors but that didn't help and when I sold the car the person who bought the car blew a head gasket on his way home.

I'd be pissed!!! That sucks bigtime. I only run 93 or 100 unleaded sometimes @ $3.05 gal. I have bought 93 my whole life, all my cars have required it, 86 cutlass w 307HO. 96 Aurora 4.0 Northstar and the 01 ssei L67. I'm used to dishing it out $$$ for gas. The bonus is that the SSEi gets the best mileage, 17.9avg mpg today. Woo hoo.

I used to have a sticker on the dash board of the 442 that said,
***, GAS, or GRASS. NOBODY RIDES FOR FREE!!!
Fun taking your friends mom to the airport. :?

Problem with your mom is those Troopers are decent "trucks" that take tons of abuse and love it. At least mine was. She got used to abusing a vehicle and having it come back for more.

You'll loose LOTS of power, and youre PCM will be constantly re-adjusting to new octane levels, which robs power, and milage. It'* worse milage to switch back and forth between 89 and say 91, then to run straight 89. DEFINETLY run your octane rating, or a step higher.

i dont recall if this was posted here or on another site or how i found it.. lol but seems appropriate.. and informative.......

http://www.elektro.com/~audi/audi/toluene.html