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Re: Octane issue - personal experience. (archive)
[ Follow Ups ] [ 5-series (E34) Message Board ] [ Msg. Board FAQ ]
Posted by dudel on August 27, 2001 at 09:43:40:

In Reply to: Octane issue - personal experience. posted by Oleg on August 26, 2001 at 23:39:45:

Sounds like you are getting some pre-ignition. At 200K+ miles, I'b bet you have a fair amount of carbon in your heads. The carbon heats up and creates hot spots in your combustion chamber. The hot spots are lighting your air/fuel mixture before the spark, thus the preignition and knocking. Higher octane is masking the problem. I'd consider running a few cans of chamber cleaner (followed by an oil change). This may let you go back to un premium fuel. If you use a premium fuel with cleaning additivies (Chevron's Techron is good stuff) you may be getting a cleaning effect anyway (just a slower process).

Don

I used to run 87 - regular but lately noticed a slight detonation on high rpms and heavy load. Over last few weeks I made a lot of highway driving with fast acceleration and this detonation started being very annoying. I poured premium to the top and all the detonation vanished. Last week I tried Silver or 89 still no detonation. I think I will stay with it.

89 525iA 219,xxx Mi (stock chip)




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