Again, I suggest that the proof is in the pudding. When you have engines that have been well used, at 300k, with only dino in them, then how can you suggest that using dino is a problem?
There's lots of examples of this around us. Audiophiles believing they get better quality out of their $300 cables, gamers thinking they play better when their monitor shows 150 FPS instead of 130 (when the human eye only registers around 70), etc. Dino oils have long been established as being fine at 3k miles, there has been some that suggest they can be run much longer than that.
As to "any body's guess," it's not guessing when you get oil reports, and there's been plenty of those if you wish to weed through the data. I don't recall seeing a single one that's said "ZOMG! Change your oil or your engine is going to blow up!" It's also no guess when 300k mile engines still run like a top, despite using nothing but dino.
Nothing wrong with being OCD and using syn, like I said, I use syn when I can get it myself. But I think it's incorrect to believe that syn vs dino is going to make a large difference in the life of the engine. Especially considering all the
other things that are far more likely to kill the engine (overheating, PHH, head gasket, EGR, etc).
Change your oil regularly and you'll be just fine running syn or dino, I guarantee it.
IIRC, the cap on my truck says 5w-30. Now it's possible someone switched it at some point, the recommendation very well could be 10w-30. Either way, it's not a big difference.
