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Octane is an anti-knock index. Nothing more.

Running a higher octane allows the computer to advance the timing (among other things) for better performance. The computer does it on the fly and it's on top of the base timing. Base timing is what you mechanically set with a timing light at the crankshaft pulley.

I run the cheapest gas possible unless I am towing, climbing hills (never in this part of TX
), or drag racing. Ok, the racing is done in another car, but you get my drift. If it ain't a knockin', don't bother with more expensive gas. It's a waste of money.

The act of introducing higher octane fuel into the engine does not produce horsepower.

Infact, it does the opposite if no other variables change. You can lose horsepower because the higher octane fuel burns cooler. When I drag race, I run the lowest possible octane. It's just like leaning a carburator out as much as possible without burning up the pistons. The leaner fuel mixture creates a hotter combustion chamber which in turns makes more power. A higher octane or richer mixture cools the chamber too much and you lose power.

Speaking of knocking ... when the computer detects knocking it'll back the timing down. In a high revving race situation that can be a vicious cycle. The engine knocks, timing is retarded, the engine overheats and knocks more, timing is retarded more, etc.

Uh ... what was the question again?


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Jim
'01 GG EX w/stuff
'93 Nissan Sentra SE-R with more stuff
 

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<font face="Verdana, Arial" size="2">Originally posted by slocko:
I can't bring myself to put regular gas in this thing
</font>
Please do. You'll save money, experience the same performance, and subtly reduce the pollution your vehicle creates (the anti-knock compounds create more nasties when burned).

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-= Darell =-
2001 Civic EX (ULEV)- currently the BIG car.
1997 EV1 (ZEV) - "This is NOT your father's golf cart"
 

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My experience with our 2000 LX Odyssey and gas is; around town we put the regular gas in it, but on trips where we load the van up and/or tow we use the medium to high grade depending on current price.

Since I my family is 400 miles away, I have driven the trip with both regular gas and higher octane gas. The vans power is a lot better on the hills and the mpg appears to be higher with the higher octane. I wish I had some real useful mpg data but each trip is a little different (head winds, driving speed, van load, number of stops) and these mpg number would become meaning less because of the variables.

FYI - I am get between 21 and 23.5 mpg on this trip.

BrianB
 

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<font face="Verdana, Arial" size="2">Originally posted by BrianB:
My experience with our 2000 LX Odyssey and gas</font>
The engines (knock sensors specifically) are quite differnet for 2002
 

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The 2002s are designed to run on regular and will not advance the spark beyond the parameter that accomodated that octane rating, so using premium will not produce more power in an '02, such as it will in a '99-'01, which is designed for premium and will reduce spark advance when knock is heard (sensed) on regular. Ol' Darell and them guys have already said this stuff, but, one can never read too much "stuff".

Jerry O.

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2001 Odyssey GG LX
 
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