AMSOIL has recently updated a Technical Service Bulletin (TSB) from 2005 discussing the use of AMSOIL synthetic lubricants in engines with possible sludge issues. In the TSB: Using AMSOIL in Engines with Possible Sludge Issues, consumers are informed that certain Chrysler/Dodge, Audi/Volkswagen, Lexus/Toyota and Saab engines can be prone to sludge formation under certain circumstances. The exact models, model years and engines are listed. Here’s the upshot:

Sludge formation is caused by oil being subjected to abnormal operating conditions such as high heat, excessive blow-by gasses, glycol contamination or poor crankcase ventilation. Sludge formation, if severe enough, can block the oil passages and oil pump pick up screen, resulting in oil starvation. AMSOIL Synthetic Oils have better oxidation resistance, detergency and dispersancy than conventional petroleum oils, and they do a better job of resisting sludge. However, they will not stop sludge formation under abnormal engine operating conditions.

If you have one of the listed vehicles, follow the OEM-recommended drain intervals. AMSOIL Synthetic Motor Oils are highly resistant to sludge formation and a terrific preventive measure for this malady, but do not push the drain interval.