Date: Wed, 02 Mar 2005 03:21:34 GMT
From: "Walt Kienzle" <wkienzle.nospamnospamlobal.net>
Subject: Re: Saab 9-3: What octane to tank?


There is a line of thought that says the lower octane fuel is more volatile and would cause more violent explosions. Higher octane fuel is more resistant to ignition, causing less violent explosions, but more importantly, fewer uncontrolled explosions that would result in pinking/pinging. All that useless trivia aside, just about any Saab I can think of that has been made in the past 10 years has a knock sensor that adjusts for octane variations. The only difference you should notice with lower octane is reduced performance (because of retarded ignition timing to accommodate the lower octane) and reduced fuel economy (for the same reason). The octane recommendation in the manual provides the spirited performance Saab owners expect and, because the recommendation comes from the factory, is the fuel used to calculate fuel economy during EPA tests in the US. The only other consideration is that high octane fuels tend to have a better additive package to help ensure that the fuel system and fuel injectors (in particular) remain clean. Not all brands of fuel hold to the same standard, but all must meet a basic minimum in all grades of gasoline/petrol that they sell (in the US. I can't speak to other regions). There are many factors that weigh in on prolonging or reducing lifetime. Given that a knock sensor controls the spark, in my opinion the grade of fuel used comes in rather low in importance on the list. Walt Kienzle 1991 9000T "Happy" <notnospamd.com> wrote in message news:4223a3ae$1nospam.microsoft.com... >I have tried 87, 89, 92 with no noticable difference, although I suspect to > feel a more little vibration when idling on 87. > > The manual recommends 92, but says it can run lower grade as well. > > The only reason why I will tank 92 would be if 87 would be bad for the > engine or shorten its lifetime. If I were to reason about this, I would > actually think that 87 causes lower heat and less violent explosions, > actually prolonging the lifetime. But I suspect it doesn't work that way > :-) > > Any recommendation, experience? > > What do you use? > > >

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