Thanks for the good information.

The only thing that I would like to point out is that using a heavier oil at a given mileage could be a very bad thing. Granted, once an engine gets worn significantly using a slightly heavier can, in some cases, extend engine life a little. But that is once it is worn. Engines wear at extremely varying rates.

An engine that goes one mile to the office and then one mile home every day will wear at an extremely high rate per mile as compared to an engine driven exclusively on long trips will wear very slowly per mile.

The sign that it is time to use a different oil weight should be the regular wear signs, not mileage. These signs are oil usage, compression and oil pressure.

My 300E for instance is at 267,000 miles and still holds strong oil pressure, uses absolutely no oil and has very good compression. Going to a heavier weight oil would actually accelerate wear during cold starts.

My $0.02,