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I guess my point was, just because machining + or - tolerances are closer, and finishes are better and smoother, really does not mean the clearances are any tighter. They aren't, at least not in the case of
that 5.7.

Relative to another comment above...at one time in the '90s it was fine to run the 2.0 Neon engine on 10w30 oil. If you took your car to the dealer, odds are good that's what they would pour in. Come 2005, and you absolutely can not run anything but 5w20 per the pwner's manual. Look up the clearances for both engines, and guess what...they have not changed over time either. I'd think if there were going to be any big changes they would show up in little 4 cylinder engines first, but even that doesn't seem to be true.

It's just something to discuss and throw around, I'm not trying to prove anything but I think the myth is funny. Tolerances may be tighter, I don't doubt that, but the desired end result is pretty much the same as always.

At the OEM level, it's not uncommon to scrap a few hundred engine blocks because the bores are oversize by like two microns. MICRONS. Pieces that could have went 150,000 miles without an issue. Sounds a bit wasteful just for the sake of maintaining tight tolerances, doesn't it?

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I did some research on the big commercial and industrial engines,and did find the clearences to be tighter and the allowable runout of componants held to near perfect tolerances.Most tolarences were held to .0000 on runout and clearences usually held to
.000 were .0008 to .0005 on a Volvo engine.