| Re: [GMCnet] Synthetic oil. Just some though's [message #282291] |
Fri, 17 July 2015 01:21  |
BobDunahugh
Messages: 2465
Registered: October 2010
Location: Cedar Rapids, IA
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Dennis Sexton brought up cold starts. Outstanding topic. In 1970 when I was attending the University of Northern Iowa. A classmate was doing a study on oil filters. And when the oil filter bypass valve had to pass oil for proper engine lubrication. ( And I'd love to remember his name ) He was only working with GM engines. Cold starts were a point of interest. So we used a Corvair engine to observe oil movement in a crankcase. So I striped a Corvair engine down to the bare minimum. Then replaced the engine block top block cover with a plexiglass cover. In this way we had a way to see how oil moved in a crankcase. That's when I became aware how fast the cam, lifters, and cylinders are lubed. It was intently. We evaluated different bearing clearances as to the amount of oil put into suspension by the crankshaft. The gears in the oil pump can be changed in just a few minutes. That's when we studied the effects of the use of high volume oil pumps. Back to cold starts Dennis. I like the larger molecules of mineral oils with the 1200 PPM of ZDDP over the smaller ones in synthetics. If your engine seals are older. Synthetic molecules will tend to slip out easier. I favor the 10/30 that GM recommended. That's the weight that GM set up the oil filter with related oil filter bypass to work the most effectively in their engines. I'm not in favor of oil additives except for engines with a new cam. There are lots of oil choices out there. You need to pick what you think is best for you. My choice is a 10/30 that has a C rating. ( Diesel ) This is for 3 major reasons.1. C rated oils can handle oil contaminants better than S rated oils. ( Gas ) Go pull the dipstick in a diesel. Pure black. 2 C rated oils can withstand more heat than S rated oils. If you get near C rated oil limits. Your engine was toast way before the oil's limits.3 Diesel engines have compression ratios of around 20 to 1. Our Olds gas engines are at 8.5. That's a load.4 I like the idea that I can buy a C rated oil that has everything my old tech engine needs. Including the 1200 PPM of zinc. And it's reasonably priced.I trust GM with their recommendations for their engines.
Some people recommend Synthetic oils in our old tech engines. I'd be interested in their reasons. Maybe I'm missing something.I recommend Synthetic oils also. But in new modern engines that the manufacture suggest.
Bob Dunahugh
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