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Re: Engine lubrication [message #355936 is a reply to message #355901]

Sun, 21 June 2020 00:46

Husker92592

Messages: 137
Registered: August 2013
Location: Temecula ca

Karma: -4

Senior Member

So,
Reason for the question and I will keep in real simple, ME being a dealer for synthetic oils for a long while now, al beit almost every car today requires synthetics, where this comes from is switching to synthetic and switching back to dyno oil "can" cause old seal to shrink.

if everything is correct and one is adding to a new rebuilt engine or existing old seals, you might want to think of replacing the seals. In no way am I suggesting these are things you should so but Synthetic oils have one benefit in that they "can" cause swelling or expansion of old seal which is the opposite of leaking.

for all those who like Dyno oil then great keep using them. in some parts of the county we dont have the advantage of benefiting from cheap anything. quite honestly I am purchasing synthetics cheaper than Dyno oil. FYI oil does not go bad its the additives that have a shelf life. This is for any oil you use.

In General for the heat and abuse we place on out coach engines you want to change your oil and filter every 5000 miles anyway. Can you go longer on Synthetic yes but that is each owners personal preference.

1974 GMC Sequoia 26'

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Re: Engine lubrication [message #357651 is a reply to message #355638]

Tue, 11 August 2020 20:50

rickmike

Messages: 252
Registered: September 2011
Location: United States

Karma: 0

Senior Member

JohnL455 wrote on Sat, 13 June 2020 13:02

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

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Re: Engine lubrication [message #357655 is a reply to message #355626]

Wed, 12 August 2020 07:29

jhbridges

Messages: 8412
Registered: May 2011
Location: Braselton ga

Karma: -74

Senior Member

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

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Re: Engine lubrication [message #357679 is a reply to message #355936]

Wed, 12 August 2020 21:47

Carl S.

Messages: 4186
Registered: January 2009
Location: Tucson, AZ.

Karma: 13

Senior Member

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

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Re: Engine lubrication [message #357702 is a reply to message #357679]

Thu, 13 August 2020 23:45

rickmike

Messages: 252
Registered: September 2011
Location: United States

Karma: 0

Senior Member

Carl S. wrote on Wed, 12 August 2020 22:47

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

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Re: Engine lubrication [message #360510 is a reply to message #355906]

Fri, 04 December 2020 11:29

roy1

Messages: 2126
Registered: July 2004
Location: Minden nevada

Karma: 6

Senior Member

I would not consider running a big block olds more then 4500 I think 4000 would be my limit not worth the chance of spinning a rod bearing.I also wouldn’t consider o-20 oil over 15 -50 in our old tech engines. A lot of stuff you read these days is for newer tech engines but that’s just my opinion.

Roy Keen Minden,NV 76 X Glenbrook

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Re: Engine lubrication [message #360511 is a reply to message #360510]

Fri, 04 December 2020 11:39

mghamms

Messages: 466
Registered: March 2016
Location: Ware, Massachusetts

Karma: 2

Senior Member

I use Mobil One 15-50 and change with filter about every 2000 miles.

When I first got it I changed the oil, whatever I had cheap, and filter every 200 miles to get the crud out.

Hopefully cheaper than a eventual rebuild.

Also every year I drain about 3 quarts of ATF and refill with new.
And suck the master brake cylinder dry and refill.

1977 Kingsley 455 as stock as it gets except lots of Ragusa parts

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