Dave with 38 Buick questions

[Guest 49340]

I have not been on in a while.  My 1938 Buick has been retrofitted with a Rochester 2GC and adapter plate.  The ignition switch is now a push button starter.  What I need to know now is in reference to the motor oil to be used in this straight 8.  The Shell 30 weight I have bought is more than expensive but is ready to pour in the car.  Are there any modern oils that are suitable for use in this car?  It may not be a daily driver but spends a good amount of time on the road.  She is not a trailer queen.  I have kept the original master cylinder, Stromburg Carburetor, choke, and rear shocks that were replaced on the car.  I will continue to hang on to them until I sell the car.

Edited June 23, 2017 by MrEarl
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[SpecialEducation]

API CI-4 (better) or CJ-4 (good) oils will do just fine and are readily available. While they are marketed for diesel engines, many also meet SM or SN specs for gas engines, too (although that's not real important here). CK-4 oils may not protect your cam from the lifters as well. Be careful of CK-4s that say they are compatible with CI or CJ. That doesn't mean they are as good as the earlier specs. If the engine is not worn and maintains good oil pressure with your straight 30w oil, than any _W-30 should do fine. The first number isn't as important as the second.

Forget brand names, only look at performance specs. That said, I recently bought a gallon of Castrol GTX for $9.99 that met CJ-4, CI-4, and SN specs. There are several Shell Rotella variants, and currently the T5 blend meets CJ-4, CI-4 and SM specs. This is always subject to change, though...

Edited June 22, 2017 by SpecialEducation (see edit history)

[RivNut]

The best thing you can is check the PPM (parts per million) of zinc and phosphorous in the oil.  Zinc is necessary for flat tappet engines, it eliminate the wear.  I've found that Shell Rotella  (diesel applications but fine for gasoline engines) or Mobil 1 synthetic 20W-50 has a high content of zinc and phosphorus.  Basic oils that meet modern standards can't fight the wear like the older oils.  Joe Gibbs has developed some great oils for his race cars, but they're very expensive.  You can get a five quart jug of Mobil 1 at Wally World for less than $25.  

 

If you start running synthetics,  you'll need to do a couple of oil changes quickly.  The synthetic oil is a good gunk cleanser.