Interesting!  Thanks for that.

Could use some updating though.

Some vehicles like Toyota Corollas are now coming from the factory with 0W-8 oil in the crankcase, and recommend refilling with the same.

Interesting how the recent trend is towards lower viscosity, when Chevrolet had already gone that route by the 1940's.

With Chev's obvious concern with start-up viscosity and lubrication at that time, I'm sure they would have been recommending a 0W-20 if modern oils had been available to them.

The Cafe numbers and getting past the warranty period is all that matters to vehicle mfts.  0 is not because it makes an engine Last longer. 

@wes-baker 

Hi Wes

"0 is not because it makes an engine Last longer"

Beg to differ.  Actually it DOES make engines last longer, and oil analysis proves it without having to wait for an engine to wear out to realize it.

Engines wear the fastest BY FAR right after start up.

It can take several minutes for oil to reach every part of the valve train after a cold start with thick oil.

So the closer your oil is to normal operating viscosity at start up, the better.

That's why nobody even sells straight grades like SAE 30 anymore.  🙂

PS

Chev knew about start up wear and lubrication even back in the 1940's.

That's why they were adamant about choosing a viscosity based on the COLDEST temperature you would encounter before the next oil change, not the hottest.

Another video worth watching, especially the oil analysis results.

https://www.youtube.com/watch?v=sALAUhldASc

And another very interesting video well worth the time to watch, by an actual tribologist.

The science of wear and lubrication can yield some surprising results!  🙂

https://www.youtube.com/watch?v=erxjPicpYyw

So what oil should be used in 207 and 235 Chevy engines?  What have others had success with?  I only drive my '36 and '56 235 ci about 1000 miles a year.  Both get an oil change each spring.  After around 12,000 miles on a NOS short block 207 in my '36 the compression test from just after break-in to present is about 20 to 25 lbs. per cylinder. Not good in my opinion.  I've always used Castrol 10W-30 because it has the reputation of not breaking down.  Any thoughts?

@randy-keil 10W30 is just fine for your 207. To get to the bottom of your compression issue I recommend you start a thread about it so your question doesn't get buried in this one.

@randy-keil I am guessing the compression reading as posted is a typo . If 20-25 is accurate  then I would be doing some serious inspecting as 120-125 is probably what the compression should be .

Sorry, I should have said the compression was 20-25 lbs lower than originally.  It was in the 110 to 120 range just after the break-in period.  I've been reading about oil additives and ZDDP and The Oil Geek states you can have too much ZDDP.  He highly recommends using what the manufacturer recommends but then in 1936 they didn't have the oils that are available today.