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Hello.
I assumed that newer engines were tighter fitting and that's how they could tolerate thinner oils.
Like early gun manufacturing and having everything fit sloppy because the machining was low quality.
What are the facts on this subject? I did a web search and crank clearance is supposedly based on journal height of .001 per so many inches.
If this is true, how is it a newer engine can tolerate a thin oil where as a outdated design cannot? The last generation of U.S v8s can hit 200.000 miles and sometimes 250,000 with just the timing chains redone. Makes it hardly worth rebuilding a classic GM or Ford V8 if you are going to drive it a lot.
Thanks for your expertise and happy holidays to all!

There has been a lot of changes in lubricants since the older V8s, in-line 4's, in-ling and V-6's and different shapes of V8 and larger designs of engines. Tie that in with material changes (always going on) and some of them have been some big changes... but the short life examples are also out there too. A lot of different styles of machining and building as well as some not to well-known tricks. (https://www.bing.com/search?q=full+flow ... 79&pc=LCTS) for example.

I played with 4's, in-line and V6's and V8s in the different shapes and had. Had some dogs as well as "WOWs over the years.

From what I have heard and read that there is a lot of hidden info about good and bad newer engines that you may get sneaky info to every so often.

Lee

Its a great question...but understand that "0W' oils are not incredibly thin. And its not mainly/only about the engine parts. Modern synthetics trend toward somewhat thinner and higher flow rates.
An example was the analysis that Lake speed Jr. did on Mobil-1 "0W-40" European car formula. He noted that viscometer testing showed that it is technically (viscosity wise) in the high end of 30wt...nearly 40 weight....viscosity wise...but that film shear strength and anti-scuff wise its solidly in the 40 weight range. It performs like a 40 weight at a lower viscosity.

A lot of things have been done to modern synthetic oils to modify flow and shear. Because they have better flow and film strength and higher temperature ratings...you do not need as thick or bulky of an oil body.

Add to that that synthetic oils have so much lower coefficient of friction....add that to modern fine grain cylinder coatings that virtually every mfg uses.....and the ability to uses thinner, lower tension ring packages.....and you can use a lighter bodied oil that also puts less drag on reciprocating parts.

Ray