Article on straight weight vs. multi-weight

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An interesting tidbit in this article I found:
http://www.busride.com/Page.cfm/PageID/8607


"Since the crank journal is constantly under load as compared to the 4-stroke engines, the 2-stroke engines require a single-grade oil with a higher viscosity. The boundary lubrication never has a chance to recover for 2-stroke engines.

In 4-stroke engines, the boundary lubrication does have a chance to recover during the non-loading turn of the crankshaft, which allows the use of multi-viscosity oils.

The use of single viscosity oil in 4- stroke engines can actually extend the life cycle with really no downside."

comments?

Now the article mainly is discussing larger engines for bus and motorcoach, but in the 80's this was how I operated a 350 cu Pontiac solely on a diet of straight 30 weight for many trouble free miles.
I know, oils have progressed so much since then and bla-bla-bla most will say, just thought some of you might find this interesting or might like to comment on the 'recovery time' as mentioned in the article with respect to boundary lubrication.
 
It is worth mentioning that in addition to extended engine life, specifically crankshafts and bearings, the peripherals such as turbochargers, air compressors and gear trains also benefit from the single grade oils. There is no need to keep two types of oils in the shop and run the risk of a mechanic accidentally pouring a multi-viscosity oil into a 2-stroke engine.

Though this has been an ongoing process in our operations for more than 10 years with the utmost success and simplicity, it is still advisable to contact the engine dealer to confirm single grade oils are acceptable before making the switch.

People may think I am crazy, but I use XHD 40 motor oil in all of my automatic transmissions and power steering as well.
I could maybe agree that monograde oil in a 4-stroke may extend it's life, provided that the multiviscosity you're comparing it to has lesser quality basestock or additive package that's more prone to breaking down and shearing under a worst case operating conditions. Example off the top of my head would be a sae30 oil vs a 5w30 oil in a boat motor in the summer running oil temps at 240+ F for sustained periods. But there are many variables and factors to take into consideration so the statement "use of single viscosity oil in 4- stroke engines can actually extend the life cycle with really no downside" is out of context and a blanket statement in my opinion. There certainly is a downside if you're starting up in cold weather.

I don't understand the loading of the bearing journal by the crank, and how boundary lube has a chance to recover in a 4-stroke vs 2-stroke. I'll admit i'm not that knowledgable about lubrication but I would think if you're method of lubrication is boundary under normal operating conditions, which the article seems to imply, then you got problems. Shouldn't it be hydrodynamic ? ... where the oil's viscosity is the proper grade so there's adequate pressure and flow to keep oil temperature at the proper level? If not then I would think it's either the wrong viscosity oil, or improper oil (basestock and/or additive package) for the application, or a problem with the design of the moving components where no oil will lubricate it properly. Isn't that lubrication 101? And i wouldn't necessarily overlook bearing design as being the majority of the problem most of the time either.

I like how the article also says: no need to keep 2 different oils in the shop and risk using a multivis. oil (i.e. the wrong oil) in a 2-stroke, then says at the end I use XHD40 motor oil in all of my automatic transmissions and power steering. That's funny! Like to know what kind of auto trans. they are. Won't be taking anything of mine there for service.

Fact is you "can" probably run a 350 chevy on just about any grade of oil. It's all about getting the proper viscosity range for the application. With a mono 30 oil, if you're not experiencing any cold startups then I see no reason why there'd be any difference of it to a recommended 5w-30 or 10w-30 multivis. oil. The key difference between the two is just cold startup temperature.
 
Perhaps thats why I had 450,000 mi on an 86 6.9 F250 . I used Penzoil HD30 since new.
 
Considering that the article mentions big/heavy stuff like busses- along with air compressors and turbos... I'm pretty sure that the automatic transmissions being referred to are Allisons. I can't say with any certainty that this is common practice to run motor oil in an allison transmission... but I'm aware of several applications in construction and agricultural equipment where motor oil, hydraulic oil, and atf can all be used depending on temperature range, year of manufacture, and customer preference. It wouldn't surprise me one bit if an 80's vintage Allison would run fine on 40wt. motor oil.

About power steering systems- MOST heavy duty power steering systems in trucks and busses specify 15W40 engine oil (though some call for ATF- especially International). I'm sure they'd work just fine with 40wt.

I'm interested to see this article... it explains why we fill all the 2-cycles here at the local detroit dealership with 40wt oil. And I thought it had something to do with the recalcitrant old farts I work with...
 
Quote:


It is worth mentioning that in addition to extended engine life, specifically crankshafts and bearings, the peripherals such as turbochargers, air compressors and gear trains also benefit from the single grade oils. There is no need to keep two types of oils in the shop and run the risk of a mechanic accidentally pouring a multi-viscosity oil into a 2-stroke engine.

Though this has been an ongoing process in our operations for more than 10 years with the utmost success and simplicity, it is still advisable to contact the engine dealer to confirm single grade oils are acceptable before making the switch.

People may think I am crazy, but I use XHD 40 motor oil in all of my automatic transmissions and power steering as well.
I could maybe agree that monograde oil in a 4-stroke may extend it's life, provided that the multiviscosity you're comparing it to has lesser quality basestock or additive package that's more prone to breaking down and shearing under a worst case operating conditions. Example off the top of my head would be a sae30 oil vs a 5w30 oil in a boat motor in the summer running oil temps at 240+ F for sustained periods. But there are many variables and factors to take into consideration so the statement "use of single viscosity oil in 4- stroke engines can actually extend the life cycle with really no downside" is out of context and a blanket statement in my opinion. There certainly is a downside if you're starting up in cold weather.

I don't understand the loading of the bearing journal by the crank, and how boundary lube has a chance to recover in a 4-stroke vs 2-stroke. I'll admit i'm not that knowledgable about lubrication but I would think if you're method of lubrication is boundary under normal operating conditions, which the article seems to imply, then you got problems. Shouldn't it be hydrodynamic ? ... where the oil's viscosity is the proper grade so there's adequate pressure and flow to keep oil temperature at the proper level? If not then I would think it's either the wrong viscosity oil, or improper oil (basestock and/or additive package) for the application, or a problem with the design of the moving components where no oil will lubricate it properly. Isn't that lubrication 101? And i wouldn't necessarily overlook bearing design as being the majority of the problem most of the time either.

I like how the article also says: no need to keep 2 different oils in the shop and risk using a multivis. oil (i.e. the wrong oil) in a 2-stroke, then says at the end I use XHD40 motor oil in all of my automatic transmissions and power steering. That's funny! Like to know what kind of auto trans. they are. Won't be taking anything of mine there for service.

Fact is you "can" probably run a 350 chevy on just about any grade of oil. It's all about getting the proper viscosity range for the application. With a mono 30 oil, if you're not experiencing any cold startups then I see no reason why there'd be any difference of it to a recommended 5w-30 or 10w-30 multivis. oil. The key difference between the two is just cold startup temperature.




bacj when i can heavy equipment the cat front end loaders and dump trucks all ran diesel motor oil in the engines, trans, power steering, and hydraulics systems. only thing that didnt have motor oil was the rear end and the shocks.
 
I think it's important to note that this only concerns diesel 2 stroke engines.
Gas fired 2T's do not have oil sumps, except for the transmission. The crank bearing journals are lubricated by oil mixed into the fuel that falls out of suspension just prior to combustion.
 
Very true. Many Allison transmissions use 30 and 40 weight oils. That's why some engine oils are rated Allison C-4 and Caterpillar TO-4 for use in power transmission systems.
 
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