Oil - What's best for late 30's straight 8

[mike39]

I just bought a 39' model 40 (special). The owner's manual reccomends SAE 20 weight oil. The closest thing I can find that is staight 30 weight. What are others using in late 30's early 40's Buick engines.

Thanks for the Help !!

[rocketraider]

I don't think 30 weight will hurt your engine unless it has never had detergent oil in it. Then you run the risk of breaking loose sludge and varnish that may have accumulated over the years, but from what I read, even that is kind of low-risk, and would take a whole lotta detergent to do that.

Oldsmobile was recommending 20 weight oil for its engines as late as 1966. I've seen it in Tractor Supply Company stores, so it's still available. http://www.tractorsupply.com/detail.asp?pcID=3&paID=1026&sonID=750&page=1&productID=27727

[Earl B.]

Just use SAE 30, and not HD30, and, no detergent.. B

[Guest stude8]

If your engine has solid lifters you have more to worry about than simply the weight of oil to use.

I have been looking for the correct engine oil for use in my 1928 Studebaker Big 6 and find that the new API <span style="text-decoration: underline"><span style="font-weight: bold">SM</span></span> grade oils have had an important additive ZDDP eliminated to help preserve catalytic convert life spans in modern cars. No regard for the pre 1960's flat tappet vehicles that need this component.

I found these items recently searching for "Non-Detergent" oil data. It is long but clear enough to understand. Print these out to read and save. * Careful, I just notiiced the guys did not use headers or page numbers so mark your copies as printed so you don't get all unrelated copies mixed up.

Read these reports from Model A owners who have I think done a thorough job of investigating what to use in their cars. I personally have located a supply of Shell Rotella T SAE30 heavy duty oil API service CI-4 grade.(Compression ignition "diesel" product "I" additive category)which still contains the ZDDP component, it was found in stock at a local tractor supply store "Rural King".

Stude8

http://rockymountainmodelaclub.org/Tech_Articles/Engine/WHICH_OIL_TO_USE_by_Andy_Wiedeman.doc

http://www.rockymountainmodelaclub.org/Tech_Articles/Engine/OIL_ADDITIVES_by_Wayne_Russert.doc

http://www.rockymountainmodelaclub.org/UPDATE_1_TO_OIL_ADDITIVES_by_Andy_Wiedeman.doc

http://www.rockymountainmodelaclub.org/T...dy_Wiedeman.doc

[bill pritchett]

Again for what it is worth, Mobil conventional oil, the 5000 mile, 10W30 says it goes back to SG for compatibility with ZDDP. I have used it for years and an sticking with it for now.