Date: Fri, 16 Apr 1999 10:54:37 -0700 From: "John Weiss" <jrweissnopsamet*NOSPAM*.com> Subject: Re: Higher octane improving performance?
If your Saab is late '82 or newer (US spec; I don't know about other countries), it has some version of APC (Automatic Performance Control). The knock sensor dynamically adjusts timing and the turbine wastegate. Higher octane gasoline will allow higher boost on a turbocharged engine, giving markedly better performance. There is probably much less noticeable performance difference on a non-turbo engine; I always used regular grade gas in my '91 900S. There is probably less of an impact on gas mileage. We notice a definite reduction of mileage (2 mpg or so) in my wife's '98 900 Turbo when using 87 octane, but no noticeable difference between 89 and 92 octane. It probably depends on how aggressively you drive -- if the APC sensor has to do its work more often, it probably will affect mileage more. -- John R. Weiss Seattle, WA Remove *NOSPAM* from address for e-mail reply Andreas van der Wal <andreasnopsamnt:want.spam.cost.se> wrote in message news:7f7hgf$jlk$1nopsamcola.tninet.se... > I have wondered in what way the octane corresponds to the performance of > the engine. I know that higher octane prevents knocking and therefore > can tolerate higher combustion which could lead to more hp. The question > is rather if I one time fill up my car with 95 octane fuel (european > values) and the next time with 98 octane fuel, how would that influence > the run of the engine.
