In the early 80's, climbing energy prices and Canadian government incentives in the form of tax rebates expanded the use of propane as an automotive fuel. As a result of the growing population of propane fueled vehicles and field reports of serious engine oil thickening in propane service, preliminary studies of engine oil performance in this service were initiated.Field test programs have shown that propane affects service severity in the opposite way to that normally expected with gasoline. Short trip city service with propane proved very mild, whereas long haul highway propane service can significantly oxidize the engine lubricant and produce serious loss of low temperature performance. In this latter type of service, satisfactory engine oil antioxidancy together with suitable oil drain intervals can be critical to satisfactory engine life. This paper reviews these effects of propane fueled engines on engine oil performance as demonstrated in field test programs.