Motor Oil Grade (Weight) Question?

Question

I recently purchased a 50's classic car. The owner's manual prescribes the use of "Multi-grade 20W-40 oil in the crankcase. This grade is nowhere to be found. What is the closest 2012 equivalent of 20W-40? Thanks

Update:

Thanks for your answers. It's a '59 Jaguar, so I guess I ought to become used to some leaks. LOL!

turkey · Accepted Answer

10w40, 20w50, 15w40 5w40,. should all work fine.  You need to research what the recommended amount of ZDDP is for this engine.  I have owned several 50s-60s cars and ran 10w30 and 10w40 with no ill effects. This was prior to the drop in ZDDP.   I now run a HDEO like shell rotella (heavy duty engine oil) in my classics.  Due to the amount of ZDDP in it.    in either 10w30 or 15w40.  Quaker State Defy is a new oil to hit the shelves that has a boost of ZDDP in it. 

http://www.bobistheoilguy.com/
http://en.wikipedia.org/wiki/Zinc_dithiophosphate

Anonymous · Answer

20W-40 refers to the viscosity of the oil when cool (20weight) and hot (40weight).  I wouldn't use anything lower (10w30) as thinner oil on an older vehicle's gaskets, may result in leaking gaskets.  

I would just run 20W50 for that reason.

Anonymous · Answer

20 /40 is for deazels any way .  50 cars used Straight 30 an 40 weight . but i would use gatstrial  g.t.x.       10 w 40  oil that what i used in old cars

PAUL P · Answer

Hi

It will do fine on 10W30.

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Motor Oil Grade (Weight) Question?

4 Answers