Date:         Thu, 15 Jun 95 14:04:22 PDT
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Dave Kautz <dkautz@hpsidms1.sid.hp.com>
Subject:      Oil temperatures

 I see that the topic of oil temps has come up again and since it is one of 
 my favorites, I'll chime in once again.

 According to one of the technical reps. at Pennzoil, 180 degrees F is too 
 cold. The explanation for this is that some oil contaminants <acids and the
 like> need to be heated to near the boiling point of water to be moved along.
 According to these folks, oil should be 210 to 230 degrees F.

 I am not, however, going to suggest that everyone who has lower oil temps go
 out and raise them. 180F seems to be a common temperature for healthy type
 1 engines. It is probably a good idea to change one's oil frequently to 
 remove contaminants that may accumulate but most folks do this anyway since
 stock type I engines don't have an oil filter either.

 Stock type IV engines appear to have a "normal" oil temperature that's higher,
 up around 210F. This shouldn't be too much of a mystery since the air flaps
 thermostat is also 30 degrees higher <190F vs. 160F>. The type IV engine was
 designed 30 or so years later than the type I and motor oil had improved a
 lot in the meantime. I don't know what a typical oil temp in a wasserboxer is,
 but since they are using hot antifreeze and water as a "coolant" I speculate
 that it is higher still. 

 My point is that one should not seek to find an "ideal" oil temperature but
 use the oil temperature as a "barometer" of engine condition and load. If an
 engine that should have a normal of 180F is running at 230F - it's in trouble.
 If an engine that has a normal of 230F is running at 180F, it's not warmed up
 yet and maybe you should take it easy.

 Things get more complicated when an engine is modified for higher performance.
 Since piston engines have way less than perfect efficiency, when power is
 increased, so is waste heat. On an air cooled VW it is difficult to increase
 the supply of cooling air and heat exchange area <fins> so subsequently   
 efforts are made to remove this excess heat via the oil and an additional 
 cooler. Not a perfect solution, but practical. So what's the right temperature
 in a high performance application? I'll go out on a limb here and say that
 it should be close to stock. I can't support this other than to say that
 the engineers at VW didn't pick the stock temp arbitrarily. For maximum
 efficiency, the engineers want the engine to run as hot as possible. This is
 balanced against keeping the parts cool enough to survive for the long haul.
 Drag racers run engines with no cooling system at all. They make tremendous 
 amounts of power and heat - but engine life is measured in minutes. Stock 
 engines, treated well, can last well over 100K miles.

 'nuff preaching. <I'm supposed to be working.....>


 Flamesuit on, standing by,

 Dave