Ed Anderson wrote:

The older I get - the more I find out  I don't know, its getting scary

{:>)

I never gave it any thought until I went looking for a local distributor

of

bulk 2 cycle oil.  Naturally I used the Internet and did a search and

found

some very interesting information.  Many of you may know this already,

but I

did not know there was two cycle oil differently formulated depending on
whether it is designed to be used in a air cooled or water cooled 2 cycle
engine.  Here is what a brief extract of the article said.  The opposite

of

what I would have thought - had I thought about it.

"Water-cooled two-cycle engine oils require higher levels of a heavy oil

to

prevent piston and cylinder wall scuffing. Because of their high average
piston temperature, lighter oils evaporate too quickly from the piston
cylinder contact area. The heavy base oil, which vaporizes at very high
temperatures, resists evaporation and remains in place to provide
lubrication to the piston and cylinder. Air-cooled oil formulations must
have much lower levels of the heavy base oil than water-cooled engine

oils.

These oils require only a small amount of heavy oil to provide protection
against piston scuffing and seizure at peak temperatures. Heavy levels of
heavy base oils in an oil formulated for air-cooled engines can cause
engines deposits"

More info at this URL
http://www.ultralightnews.com/features/oilworks.htm

Don't know if it really matters or whether the rotary engine combustion
chamber heat characteristics would be more like the water cooled or air
cooled piston engine. FWIW

Ed Anderson
Matthews, NC
RV-6A N494BW
eanderson@carolina.rr.com

Ed,
Probably because the water cooled engines have tighter tolerances.
George (down under)

 
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