[333pg333]

ps this is supposedly a quote from a 951 owners handbook. I have heard that Porsche USA pushed M1 more than some other countries and it could also be that the US owners manual reflected this. I'm not sure of that of course.

"Low viscosity oils reduce friction in the engine. Porsche approves only low-viscosity oils which are structurally so stable that they can be used in Porsche engines both as summer and winter oils (see chart of areas of application for oils of different viscositiy) These conditions are currently fulfilled by synthetic or hydrocrack low-viscosity oils."
"Engine oil is not only a lubricant, but also serves to keep the engine clean, to neutralize the dirt which penetrates into the engine through combustion and to protect the engine against corrosion.To perform these functions, the oil is provided with addatives which have been specially developed for these functions. So-called mineral oils are produced directly from crude oil. The oils can be further refined (hydrocrack oils) or totally converted through a number of chemical processes (synthetic oils) These oils are structurally more efficient and require fewer additives than simple mineral oils.
The efficiency of an oil is expressed, for example, by the API classifications which are divided in to categories "S" and "C". The degrees of quality are expressed by the final letters in alphabetical order: the requirements for Porsche engines are API class SE/CC to SF/CD."