<VV> Re: oil engineer - oil temp

[djtcz at comcast.net]

> Synthetic oil addresses the oxidation as it will handle higher 
> temperatures but that is about the only advantage of synthetic...so...in 
> short, using synthetic does NOTHING to allow a longer drain interval. 
> just as long as synthetic under those conditions. The single advantage 
> of synthetic is it's ability to operate at temps above 305 F without 
> oxidizing rapidly. Since there are few applications where the oil gets 
> that hot the advantage is moot and contributes zero to extended drain 
> capability. Even my CBX with a partial fairing blocking part of the 
> engine never gets the oil to 300 even running on the freeway at 80 in 
> summer weather...I've checked. 

Which forum is that ?  I'd like to get in on the discussion.

I don't use synthetic for the benefit of the rod and main bearings.  I use it for hot areas with no appreciable oil flow,

Oil temp gages report bulk average oil temp.  I think there are some hot spots in there that an oil temp gage knows nothing about.
- I figure >>some<< of a Corvair's (or CBX's) oil gets nearly as hot as the cylinder head, areas of which I'm confident get much hotter than the thermistor that get over 300 F all the time.  The underside of the piston must be hotter still.  
www.sacskyranch.com/piston_normal.jpg

In 1948 NACA felt the underside of a big 5.5 inch piston might get over 500 F, according to this -
http://naca.larc.nasa.gov/reports/1948/naca-report-895/index.cgi?page0006.gif

By 1973 Japanese University researchers were reporting this.
http://www.bridgestonemotorcycle.com/documents/l-ring_effect6.pdf

The trace of oil that gets to the exhaust valve stem must also have a real tough time.  Also hard working non-flowing areas, like timing chain pins.

I'm pretty sure Oil's volatility can result in extra oil "use."  If the the oil tends to leave those hot spots it can't be good.  So I figure synthetic is much more likely to stick aroung when the going gets tough.  First by reduced volatility, second by maintaining viscosity above the 212 F SAE test temp.