Where is the proof, stated by a manufacturer of an engine. Come on if you state old wive tales as facts, you need to supply conclusive proof of it.
It's not an old wives tale. If need be, I'll find some facts and post them here if it will satisfy you.
I know plenty of them coming out of the factory with syn in it. Also check out Mobil and Amsoil websites.
And as I stated, those engines were engineered to run on synthetic oil.... different crosshatch on the cylinder walls and different rings.
You proof is based on the story that an engine needs to break in, and therefore more friction is required. If the engine rings dont break in, it does not seal properly and can cause blow by. Got nothing to do with slipperyness, and slippery oil seeping past. However this not really true anymore.
It's still very true. Even your brand new 4Runner engine needs to break in the rings properly--even if you continue to use conventional oil forever.
I've built engines before and I know for a fact that the rings don't wear into the cylinder walls immediately.
I ran my V8 for 20k on dino, just to be safe. But had no real reason to do so.
Sounds kinda hypocritical to me.... why be safe when you know for sure that you don't need to break in your engine before switching to synthetic??
I have rebuild and raced many engines (stopped doing it about 10 years ago) and even then there was no real proof of the break in theory. SOme guys just ran their engines hard straight out of rebuilding them, with no ill effects.
The break in theory is controversial.... but that has nothing to do with synthetic or conventional oil. The break in theory is basically guys who hammer their engines from the first mile vs guys who don't do that until a few thousand miles.
Yes cars do tend to peform better after a few miles, but lots of things need to break in not justthe engine.