Site News - 1/3 Member of the Year: DougM
Date: Sat, 11 Oct 1997 00:13:42 -0700
From: Alan Mittelstaedt <>
Subject: Re: Premium Gas

Saab85900 wrote: > > >Aaron King wrote: > >Using high grade fuel in your car, even if it does not need it, will help keep > the valves and piston clean. You can get carbon build up with lower octane > which will eventually cause power loss. > > Wrong--use the octane recommended by the manufacturer. Use of a higher than > required octane can cause carbon buildup. > Most of the carbon buildup will be on the backs of the intake valves, and that > comes with any grade. > > Use a product made to clean things--AMSOIL PI or BG 44K are the best I know > > Dick in Falls Church, vA > 85 Saab 900 turbo High grade fuel is not necessarily high octane, but the two usually go hand in hand. Carbon buildup is caused by excessive aromatic hydrocarbon (VOC) and/or sulfur content, which is usually found in less expensive fuels. Octane only indicates a fuel's resistance to detonation; not its flame speed, specific gravity, VOC quantity, or sulfur content. High grade fuels typically also contain detergents that help keep intake valves clean. Using a concentrated detergent may dislodge large particles and damage valve seats, piston crowns, and ring lands. I would recommend frequent tune-ups to ensure that the engine is operating at peak efficiency, and find a fuel that produces a good spark plug reading. The engine will then keep itself clean, or gradually clean itself up. For the worst carbon buildup, cylinder heads must be removed and the carbon removed manually. Using a detergent in this situation could severely damage an engine.

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