Valve Seat Recession - An Independent Review of Existing Data

The mechanism of valve seat recession is well understood and a review of the existing literature shows that it consists of two processes - the generation of hard particles that then grind or abrade the valve seats. Metallic fuel additives can prevent recession by stopping the generation of these hard particles. Both new and previously published data are presented to demonstrate that low concentrations of all the commonly available additives provide adequate protection for most service applications. However, the data also show that severe testing with low treat rates will produce valve seat recession. The author argues that, if sufficient concentration of additive is used, the initiation of recession is stopped under extremely severe conditions and alternatives to lead can offer complete protection.

The paper concludes that the use of lead replacement additives should be at the maximum possible level commensurate with all aspects of engine performance. There are no standard tests for valve seat recession and, as a consequence, the additive supplier must be responsible for recommending dose rates that do not lead to potentially harmful side effects.