Lubricant Ash Content and Surface Ignition in Gasoline Engines

A testing technique has been evolved using typical United States and European production multicylinder gasoline engines to assess the effect of quantity and type of lubricant ash on surface ignition. Results indicate that, for a given metal type of additive, high-ash lubricants have a greater propensity to surface ignition than corresponding low-ash blends.

Tests at a constant ash level show magnesium-based lubricants to be less prone to such problems than barium- or calcium-based lubricants.