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Good and Good enough Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 7 Aug 2002 10:39:47
In Reply to: 93 vs. 94 octane: Opinions???, Joe98, Wed, 7 Aug 2002 10:28:25 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Time for the Octane story
Octane is a rating of the knock resistance of fuel. The higher the number, the more resistant the fuel is to knock.
The Saab engine will vary performance to compensate for, among other things, fuel octane differences. If the engine control detects knock (actually, in a '98, the precursors to knock) it will adjust timing and boost.
A lot of things affect knock - engine load, outside air temperature, altitude, engine speed. A big one is the engine. Each one is a little bit different.
What you want to do is run the lowest octane fuel that gives you full performance. The engine control dials back performance if it detects knock. Once you are running a high enough octane not to knock under all conditions, that's the most you'll get. More octane won't produce more performance. The engine control doesn't increase boost to take advantage of higher octane.
So If you get full performance on 93, then the extra octane rating of 94 is a waste of money. Every engine is different, and those differences increase as cars age. Some engines become more immune to knock, others more sensitive. I have two older 9000T's that give full boost on 87 octane. Great! I get NO performance increase with 89, 91 or 93, so I get to use the cheap stuff. I had a 900T with basically the same engine, and it required 93 to get full performance.
Unless you see a performance increase going from 93 to 94, don't spend the money. And even if you do, decide if the performance increase is worth the money. You won't be damaging the car running 93.
Silly question - how does the car run on 91? or 89? Run a tankful. If you don't notice a performance decrease, then run lower octane and save money.
Good luck!
posted by 140.157.4...
, Wed, 7 Aug 2002 10:39:47 <-- Viewing This Message, Wed, 7 Aug 2002 16:15:09
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