| 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
Karma: 11
|
Senior Member |
|
|
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
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
|
|
|
|
| Re: [GMCnet] Synthetic oil. Just some though's [message #282302 is a reply to message #282291] |
Fri, 17 July 2015 08:17  |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
|
Senior Member |
|
|
I'll add a couple of observations and a question to this.
My experience with Diesels has been, prechamber engines blacken the oil way quicker than non-chamber engines. (Old VW turbo diesel vs TDI diesel, original Oldsmobile diesel vs many stationary power plant engines) The newer VWs and my several Cummins and Dear Johns act much like a gas engine - the oil darkens over time... but the old 1.6 turbodiesles any my old Jettas turned the oil to ink in a hundred miles. Wonder why?
Next, what's the difference in Aero oil and automobile oil? Other than that it may not be available in a light enough weight for an auto engine. After initial runin, we always put Aeroshell AD (Ashelss dispersant) oil in flat motors, pretty much everybody did. Can one of the gurus 'splain the difference, or is there any? I ran my Corvair on Aeroshell 80 (40 weight) for many miles without any oil related problems. Mostly because I was broke and the oil was free. Everything else fell off the little junker one time or another, but it never had oil related problems.
thanks,
==johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
|
|
|
|
|
|
| Re: [GMCnet] Synthetic oil. My thought's [message #282309 is a reply to message #282291] |
Fri, 17 July 2015 10:24 |
Ernest Dankert
Messages: 133
Registered: May 2007
Location: Ogden, New York
Karma: 1
|
Senior Member |
|
|
I use AMSOIL in anything with a gearbox or engine. My '98 Silverado had cold start knock, the #1 cylinder was bored large (manufacturing defect) that allowed piston slap when the temperature got low. GM would do nothing, it was an aesthetic defect. With syn blends the knock would be evident at a lower outdoor temperature. With Amsoil it was the lowest, a good 30* lower than with mineral (dino) oils. Careful test records confirm 10% mileage increase with engine and 15% with engine, transmission, and differential. My daughter left the fill cap loose on out V2 Kohler garden tractor and mowed the lawn with very little or no oil (I could not tell!). We use this tractor to this day, 6 years later due to in my mind Amsoil protection. Our '98 Venture was changed to Amsoil at 128k miles and when the 3600 hundred head gasket blew, the servicing mechanic knew about the synthetic and he was confident the bearings were OK. I put a high volume oil pump in my '77 Corvette (real long story) and the oil pressure profile was goofy (high at start, low at idle, NEW bearings) and Amsoil gives me steady oil pressure. I think it was a stuck oil relief but unsure. In our daily drivers (4) I change the oil and filter once a year, warranty or not. Lawn mowers, garden tractors, Ag tractor, Corvette, Silverado, HHR, Impala, Equinox, generators (3), pressure washer. I do not have issues with seal leaks, if you convert from mineral oil, use a engine flush or change the synthetic at 5-7k miles the first time.
Air cooled engines run hotter and a group IV oil, synthesized from natural gas (Mobil 1 and Amsoil) has a higher flash point and will withstand the heat better. Multi weight engine oils will oxidize the viscosity modifier and you will loose the high viscosity protection. If you are intent on using a mineral oil in air cooled engine, my thought would be to use a straight weight oil.
Diesel engines use C rated oils to hold the carbon in suspension longer and to tolerate the fuel oil contamination. C rated oils are backwards compatible to S rated oils. With oil analysis and bypass dual stage filtration it is possible to gain extremely long oil change intervals.
I am not an Amsoil dealer, I am a preferred customer and purchase at dealer net. I place my order online and UPS delivers it in 2 days. In my world the extended drain and mileage improvement pays for the better quality oil. The added lubrication protection is comforting.
1977 Eleganza II
Ogden NY
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
