Gas Engine Reliability: Understanding Engine Oil Consumption

Nov 16, 2002
Good article. Importance of good ring seal in an engine to keep blowby down as much as possible. Blowby really impacts your OCI.

Thijs Schasfoort and Clinton Buhler are senior technical services advisors for Petro-Canada Lubricants.

"The above explains that the ash throughput must be controlled by finding the correct balance between oil consumption and oil ash content. The target is to provide sufficient ash throughput and ensure the lifetime of the cylinder heads while at the same time keeping ash throughput low enough to prevent excessive fouling of the combustion chamber, heat recovery boiler, and exhaust gas catalyst, all of which could cause engine downtime and cost significant money to rectify."


This paper has explored the mechanisms of oil consumption in gas engines, including pathways through the piston ring pack via inertial throw-off and reverse blow-by, valve stem and turbocharger seals, crankcase ventilation, and lube oil volatility. We have demonstrated the influence that the lubricating oil film thickness plays: A thicker oil film contributes to more oil being carried past the ring pack and a thinner oil film allows more oil to pass through the valve stem/guide interface and turbocharger seals.

For a stationary gas engine, choosing a lubricant with the correct ash level is extremely important in order to provide sufficient engine protection while not producing excessive ash deposits. The total amount of ash passing through an engine is not only a function of oil ash content, but also very much a function of oil consumption. Understanding and monitoring daily oil consumption rates provides critical insight into engine reliability and helps in identifying conditions that may contribute to premature wear. It is a necessary tool that complements used oil analysis, filter analysis, and visual inspections.

A stationary engines operating parameters are different than an motor vehivles operating parameters. Just think Italian tune up. or water cooled vs air cooled two stroke deposits and additivec deposits especially with the old formulation used.