on the road again,
I'm not sure what you are trying to do on the engine, but usually you don't just replace mains and rods. The inserts would be worn AND the bearing surface of the crank as well. All this, if done properly would require grinding the crank and precise measurement of the journals.
This is a engine builders arena.. I think the most a guy could do by himself under a shadetree would be to remove main bearing shims and use a plastigauge. This would require that your truck had main bearing shims...I don't know if yours does!
I think the loss of "magic" in the multi-grades was a reference to the viscosity index. Oil chemistry is complicated, and it is easy to come to conclusions based on poor information.
I can't believe the oil companies would invite litigation by pumping out a product that went sour in 1500 miles, when the common oil change interval is about 3000 plus miles. I might be naive though.
Stuart
