E: Engine Oil Viscosity

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wmg73141

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Non-VOC Member
This thread has reminded me that many years ago I was "invited" to attend a lecture by an expert on Tribology. (Students are reluctant to give up valuable drinking so I was "volunteered", with others, to swell the audience numbers so that the poor fellow didn't feel lonely.) As it happened the guy knew his subject and the lecture was very well worth the time spent.

One thing I particularly remember was his comments on multigrade oils. He explained that viscosity was maintained by the creation of what he described as large molecules of oil like "balls of cotton wool". The problem, at least at that time, (late '70s), was that heavily loaded sliding surfaces tended to smear the molecules out of existance. Aparently they do not reform, the oil still lubricates but over time it becomes effectively a single grade oil.

Not much help maybe but may go some way to explain why regular oil changes are cheaper than engine rebuilds.
 
vibrac

vibrac

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I will rephrase my question what make of zddp is on sale in UK?
It would seem if available it would reduce hand wringing at the garage
 
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clevtrev

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wmg73141 said:
This thread has reminded me that many years ago I was "invited" to attend a lecture by an expert on Tribology. (Students are reluctant to give up valuable drinking so I was "volunteered", with others, to swell the audience numbers so that the poor fellow didn't feel lonely.) As it happened the guy knew his subject and the lecture was very well worth the time spent.

One thing I particularly remember was his comments on multigrade oils. He explained that viscosity was maintained by the creation of what he described as large molecules of oil like "balls of cotton wool". The problem, at least at that time, (late '70s), was that heavily loaded sliding surfaces tended to smear the molecules out of existance. Aparently they do not reform, the oil still lubricates but over time it becomes effectively a single grade oil.

Not much help maybe but may go some way to explain why regular oil changes are cheaper than engine rebuilds.
Click to expand...
Basically the long chain polymers that make up the high viscosity factors break down ( chopped up) because the oil never gets to its operating temperature. Oil designed for engines is wanting the oil temperature to reach a certain temperature for it to become a lubricant that puts a film between the surfaces. That temperature is in the region of 170 F. Until it gets to that temperature damage is being done. When did your oil get past 50 F ?
Years ago when I did a temperature check on all bikes turning up at a Liphook meet, I had a page full of figures quoting Oil used, distance traveled to meet, bike capacity twin/single.air temperature. Next day spoke with Filtrate told them what I had found, and asked for a recommendation of oil to be used, the answer `Straight 10.
If anyone asks me what I use, it`s 10-30 diesel.
My experience of riding in high temps, (1oo F) I found I could still dip my finger in the tank without burning. Try that in your car after ten miles.
 
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timetraveller

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I remember going to a lecture by Ted Hampshire, when he was a rep for Filtrate. It might have been partly tongue in cheek but as I recall it the story was as follows. A multi-grade oil was thought to be a good thing but the compound which provided the thickening was essentially a varnish. Varnish is not a good lubricant so graphite was used to overcome the 'varnish' which was there to try to provide a constant viscosity. Oh what a tangled web we weave etc etc.
 
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