[doug7x]

Now, I do understand the "not draining fast enough" burned valve theory, & although this makes sense, it is NOT the reason to use the lightest possible viscosity oil. Fact is, 99% of engine wear occurs during cold starts (by "cold", I mean the engine not at operating temp, not just the outside air temp.) The thinner the lube (lower viscosity), the sooner it will be pumped to where it needs to go, thus lubricating all of our moving parts sooner. With the synthetic blends available today, the film strength is far superior to the stuff we used years ago. ( I used to SWEAR by Quaker State 20w40 deluxe...I could easily get 120-150,000 miles on my old small block Chevys...Now I'm using Valvoline 5w30 dura-blend, & putting twice the miles on an engine turning 2 or 3 times as many RPM on the highway. I'd be willing to bet that if I had been able to use this stuff back in the 70's, those old SBC's would run over 1/2 million miles) Hope this helps