I did a test with an inclined piece of metal with a drop of M1 5w30, Citgo Synthetic 10w30, and Delo 400 sae 30. At room temp the next day, i could only see the straight weight oil on the inclined block. The 2 synthetics ran off. Is this because it was at room temps, or would this be differnet if the oils were heated to 212?
Which clings better?
- Thread starter JonS
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I ran across an article explaining why single weight oils are kind of coming back in aircraft, although for many they never left. Private aircraft especially tend to have a lot of hanger time, and thick single weight oils cling better than multi-viscosity oils, helping to prevent rust. Synthetics came and went kind of quickly for other reasons.
So, would a single weight oil reduce startup wear in a car engine?
Not likely. With a warm engine, it's going to wash down just like a multiweight.quote:
Originally posted by bighead:
So, would a single weight oil reduce startup wear in a car engine?
A layer of antiwear additives is supposed to help reduce metal to metal wear at startup, I think.
Not a given if it doesn't flow as well as a multi-weight when cool. Whatever the theoretical advantages of straight weight oil, presuming it's hot at shutdown time, it will drip back into the crankcase. When the engine's restarted once cold, the only lubrication for the first critical seconds will be what little oil's still clinging to the sliding metal parts. The time without oil flow through the galleries could be significantly extended with a slow-flowing straight weight - to the point of nullifying whatever theoretical advantges a cling-prone straight weight oil presumably offers. Also keep in mind that aircraft engines are mandated for general overhaul at specific operation time intervals - whether they're "shot" or not. Car engines aren't.
But only if placed there at ambient temps. ZDDP protects metal surfaces at startup.quote:
Originally posted by JonS:
I would think it would reduce start up wear.quote:
Originally posted by bighead:
So, would a single weight oil reduce startup wear in a car engine?
The term your refering to is "repose angle". It is a measurement that measures the angle of the fluid drop to the substrate and is done with a micrometer incline plane and a microscope. You are measuring the apparent surface tension of a liquid at a specific temperature on a specific substrate. This is really tough to do in my garage and if I try it there are so many variables that the results are bogus. IMHO
Lithium Grease would out cling all those oils but I wouldn't put it in my crankcase.
At 212°f all those oils are going to slide right off of metal surfaces and into the pan. What they leave behind is a function of the additives and or polarity not viscosity. ALso I think surface tension is probably bad in a motor oil, I want it to spread quickly over metal surfaces. Try the expirement with a flat plate lefel and drop the same amount of oil of differning types. The ones that spread the fastest are better.
General concensus is that most wear occurs at start up. Exact percentages are difficult to prove, but at least it is substantial.
That straight weight isn't going to flow like the multi when you need it the most. Cold start up can be 0 or 100F - I want flow then. When it's hot, they are virtually the same.
That straight weight isn't going to flow like the multi when you need it the most. Cold start up can be 0 or 100F - I want flow then. When it's hot, they are virtually the same.
hot engine bearings etc.motor oil runs away from a hot surface...
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