There are a lot of comments I COULD respond to, but I'm tired after this week's travel to Tulsa and back and I don't want to argue with any of my friends on Crossfireforum - so I will say this:

In 1994, I bought a new pickup, a GMC 1/2 ton with a 4.3L V6 in it. On the oil cap, it said, "5W20". I ran 5W20 for 10,000 or 12,000 miles, but I hated how the oil pressure would drop to 5 pounds at idle. I mentioned this to Galen, my older half-brother who had just retired from GM after 30 years. He was trained at GM institute DECADES before as an engineer, but ended up running various GM plants in Michigan. His response to me was:

"Mark, the significance of low oil pressure at high temperature is not all that alarming when the engine is new. Oils today lubricate better than in, say 1950. However, the recommended oil is based on factors in addition to engine wear. We have to meet the gov't mileage standards as well -and every little bit counts. A thinner oil is easier to pump and can save a TINY bit of mileage, but again, taken together with other measures, it all adds up. A thinner oil also protects the engine better at start up when most wear occurs, and for most drivers thinner oil serves them well as they often NEVER get the car to operating temperature running errands, etc.

But as an engine ages and wears, oil pressure drops due to sloppyness in bearings that occurs over time as the oil passes thru tolerances in, say, the crankshaft - this means less flow is available at the far end of what ever route the oil is taking. In this case, a heavier oil is recommended (this is where the designation "high mileage oil" comes from).

I then remembered the Ford vans we ran at Troup Electronics - they used cheap 10W30 oils in them and by 150,000 miles you could hear the rattles in the crank at idle, due to the low oil pressure and the wear that had occurred over the years. Could I avoid this in my own vehicle? I thought so...

Back to my pickup. I was warned by several mechanics and even more well-meaning but obviously ill-informed friends - "if you put heavy oil in that engine, you'll ruin it. These engines today are built to very tight tolerances, and you need a thin oil to get thru those passages." Sound familiar?

Anyway, at 10-12K, I moved to 15W40. I observed much better oil pressures. Somewhere around 150,000 miles, I went to 20W50. I sold that truck to my best friend, Ed in 2000 at around 232,000 miles. He runs 20 in the winter and 30 in the summer (yea, strait weight detergent oil!) On March 24, 2012 (my birthday) he sent me a cellphone-taken picture of the odomoter as he drove to work - 408,000 miles. The truck has had two radiators, many u joints, two wheel bearings, a fan motor, two water pumps, at least one heater core, one distributor and several sets of brakes replaced. But the block itself just goes on.

Run what ever oil you want to. Take or leave my advice in this thread - I'm good with it. But there is nothing so valuable as something learned from your own 53 years of life experience. This is what I have learned, and I live by it. No, I won't be putting 20 or 30 weight oil in my car - but 5W50 serves me well.






Oh, one more thing, Ed replaced the clutch at 390,xxx miles - because a bolt broke off! The clutch was still useable but since they had it apart, they replaced it.