On engine deposits...

Joined
Feb 9, 2005
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2,199
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Arizona
I have read, possibly at the Chevron website in years past, that deposit formation is quite different with unleaded gasoline from what it was with leaded. The information I read said that leaded fuel built up deposits rather quickly, but that the overall deposit levels stabilized after some number of thousands of miles and pretty well stayed there. It went on to say that with unleaded, initial deposit formation was much slower but that the buildup essentially never stopped. This was almost certainly in the '90s sometime, so it should have accounted for detergent-additized gasoline. Has anyone else read this article/information? I cannot find it anymore.
 

Kestas

Staff member
Joined
Jun 4, 2002
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14,037
Location
The Motor City
I read a similar article 20 years ago. They talked about flow around the valve. They claimed the deposits that collected actually helped with the flow and led to higher running efficiency, that leaving the deposits is desirable during engine rebuild, and that race car engines try to mimic this feature by building cone-shaped valves. I never heard verification of this phenomenon since.... and I did not leave the deposits when I rebuilt my 71 Olds 350. This somewhat relates to your question since I believe the deposits are forming on dead spots as related to air flow.
 
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