Engine lubrication

[richard michelhaugh]

> J.R. If GM says 10W-30 then what is your logic that 20W-50 is “better”? Seems it would exasperate the gravity drain back issues. Most
> builders today don’t like heavy oils as they pull less heat from bearings and heat kills soft bearings

The oil GENERATES the heat in hydrodynamic bearings The more viscous the oil, the more heat is generated in the bearing and the thicker the oil film
that separates the shaft from the shell(up to a certain point). And yes, it carries the heat away too.

They use lighter weight oils today to generate less heat thus less friction losses. The bearings are designed for the lower viscosity oil.

Rick Michelhaugh
--
1974 26' Canyonlands
aka "The General"
Clinton, TN

 

[johnny]

In the 70s, I spoke to guys at airshows. Most of them, and they said the racers as well, used reprocessed oil in the airplanes. They weren't worried
about additives, the oil was changed every day at least, and for the racers every flight. They said the oil was 'oilier' in that it had been refined
three times - initially, in the engine, and again at the reprocessor's. This supposedly breaks down the molecules even smaller, giving better
lubrication. That was their story anyhow.

--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

 

[Carl Stouffer]

The machine shop in Tucson that did the work on my 455 (Larry's engine and Marine) said that, due to the large size of the main journals on the 455
crankshaft, they set the clearances for 20W50 oil. I'm not totally clear on the reason why, but it has to do with getting enough oil in those large
diameter bearings. I broke it in with 15W40 Rotella, but imediately switched to Valvoline 20W50. I would be comfortable going back to the 15W40, but
think maybe the 20W50 is a better choice for me in Southern AZ, where I am often driving the coach in 100 plus degree temps, at least during the
Summer.
--
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles,
Solar battery charging. GMCSJ and GMCMI member

 

[richard michelhaugh]

> The machine shop in Tucson that did the work on my 455 (Larry's engine and Marine) said that, due to the large size of the main journals on the
> 455 crankshaft, they set the clearances for 20W50 oil. I'm not totally clear on the reason why, but it has to do with getting enough oil in those
> large diameter bearings. I broke it in with 15W40 Rotella, but immediately switched to Valvoline 20W50. I would be comfortable going back to the
> 15W40, but think maybe the 20W50 is a better choice for me in Southern AZ, where I am often driving the coach in 100 plus degree temps, at least
> during the Summer.

I'd like to see how he determined clearances for the 20W50 oil! Since I studied tribology, I know that it is a pretty complicated process to properly
design a bearing for a particular weight oil.

Rick Michelhaugh, ME
--
1974 26' Canyonlands
aka "The General"
Clinton, TN