Questioni recently bought my first car, a 72 Pontiac Lemans.I'm about to change the oil and i looked on the dipstick and found out it takes gm 60 41-m ms type oil. what it doesn't say is what viscosity, so my question to you is what viscosity oil would be best for my Leman's v8 350. Also would it be a detergent or non detergent oil? -THANKS A LOT-
AnswerBack in those years, they did not give a recommended viscosity because they would not have known what part of the country you would be living in, and the viscosity recomendation is different for different driving conditions.
The old GM specification for oils has been obsolete for years, and oils have improved tremendously. Also, there is almost no availability for non-detergent oil anymore, and I would not recommend it even if it were easily available.
If you live where it never goes below 32 degrees, you should use either SAE30W oil (NOT 10W30 or 5W30, that is way too thin!), or 15W40 oil. 30W oil is getting hard to find also, but NAPA stores still carry it, and it is rated service SM - which is much better than the old MS rating, and fine for your car. If you cannot find that oil readily, buy the 15W40 that is labled that it meets the specification for modern Diesel engines - that is the best oil now made for our old cars.
If you live where it DOES get much colder than 32 degrees part of the year, in those months, you can safely use a thinner oil (SAE20W) or 10W30, but don't go to anything thinner than that, and get it out of the engine when the weather warms up.
If you live where it gets really hot, for instance in the southwest desert where I live, use SAE40W, or the 15W40 only - anything else is too thin.
Dick
