I've been using straight 30 weight oil in my '34 during the summer months. After some discussion with some local guys I'm thinking of going to 40 weight. I would love some opinions, pros, cons, etc. from any of you here. Thanks ahead for replies!!!

I am a believer in 10w30. I believe Chevrolet actually recommended 20w when the cars were new. Are you considering 40w to reduce oil consumption? I think that is too heavy for these old engines and lighter weight oil will get to the bearings faster on start up and provide better over all lubrication. JMO

YF,

I recommend you avoid the local guys. Take back streets on the way out of town. Find some guys over on the next summit who know what they're talking about.

In any case, whatever you use, other than Uncle Ed's recommendation, make sure it has a 10w in front of the other number.

Remember: Your engine is a part splash system and that the main purpose of oil is to effectively carry off heat while not being diminished (used up somehow) in the process.

Best,
Charlie

The cylinder walls and wrist pins are lubricated by an oil mist created when the dippers pass through the troughs. With high viscosity oil the droplets produced are too large and settle back into the oil pan without sufficiently lubricating those parts. Yes you can reduce oil consumption while destroying the wrist pins and wearing the cylinder walls/piston rings. The choice is yours. Instant gratification with lower oil use or future disappointment and confusion on why the engine had to be rebuilt.

I think 40W oil is too heavy for any early Chevy in any weather. Check your owners manual.

Mike

Thanks for all the replies. I guess Ford folks think differently than Chevy folks. So, to quote a line from one of my favorite movies, "Oh Brother Where Art Thou", I'm with you guys.

I wouldn't use 40wt oil in any Ford I owned either. !0-30 lubes best. 15-40 when it gets worn a bit.

#40 oil was specified for Ford V-8 engines in the 1930's. It had something to do with their thirst for oil. The same engines wore out their cylinder walls, was the #40 too "thick" for good cyl. wall lubrication?
#40 was specified for many cars in the 1930's.

I would not use 40W in there. If you are burning a lot of oil it could be leaking more than burning. May you just need new gasket set on pan and side pan or valve cover. Or if your rings are that bad it is time for a re-build. Do you have blow by?

Note that #30 , #40 and #50 oil does not have a "W" after the number. The "W" stands for winter and the cold weather flow rate is not done on #30 and heavier oils because they are not a winter oil.

I use 10w30 or #30 in the cars....#30 is getting a little harder to find around the Portland area. If you call the Chevron tech line I bet they will tell you 10w30 or #30. That tech line is really good for when you have questions.

The problem with oil company tech lines is that they are not familiar with the unique lubrication requirements of our pre-WWII Chevys. I bet the vast majority of those answering questions haven't even heard of a splash or dipper engine lube system. They understand piercings and tattoos better than babbitt engines.

Also a thicker oil is not easy for weak wipers and rings to wipe the oil off the cyl. walls and causes more oil to burn.