oil degradation

[mick281]

Hi , Further to another post on here (low oil pressure when hot at idle) i,d like to ask if 15w/50 oil can permanently lose it,s viscosity if over heated ?

[desmo]

Yes it can.
All mineral based oils can degrade & break down over time either due to overheating, contamination or infrequent changes.
That is where fully synthetic oils win, they do not degrade to the extent of mineral oils, provided you use a synthetic oil designed for a wet clutch. (Shell Ultra)
I always use fully synthetic oil, although it's expensive, it will keep the engine in prime condition with minimal wear.

[slob]

My understanding is basically it's the length of the chains of hydrocarbon molecules that provide an oil with lubricating and load bearing properties. These chains are broken into shorter lengths with age and during use. With Synthetic oils it's possible to make longer chains in the first place, hence they are generally regarded as a superior product (if not entirely suitable for wet mutiplate clutches).

[Capo]

All oils have a finite temperature above which their structure is damaged

[Nickj]

The top of the piston, around the rings, will be around 150 - 200 C. This is where the semi and full synthetics win as they don't degrade as fast as normal mineral oils at temperature. The long chain polymers get short as they are boiled or chopped to extinction in the engine, this is the sludge you find in motors. These will be a component part of the synthetics and are usually the additives in mineral oils.
Older mineral oils were maybe tougher and kinder to motors as they had additives like zinc (ZDDP) now only there in traces as it kills cats.

[eljaybe]

I found this very long post on another forum, all about oils, some of it a bit of an eye opener...

http://www.ducatimonsterforum.org/index.php?topic=1912.0

Sounds like shell ultra isn't 100% fully synthetic.

Never really too sure if what you read on forums is true, but this guy does seem to know oils.