Date:         Thu, 19 Nov 1998 02:06:38 -0600
Reply-To:     Blue Eyes <lvlearn@MCI2000.COM>
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         Blue Eyes <lvlearn@MCI2000.COM>
Organization: Vexation Computer
Subject:      Re: Thermostat - 80 vs 86 degree
Comments: To: Roy Mellor <roym@ARISTOTLE.NET>
Comments: cc: vanagon@VANAGON.COM
Content-type: text/plain; charset=us-ascii

Roy wrote:
"What are the benefits of using an 80 vs 86 (stock) degree thermostat?
I ordered the 80 degree one thinking cooler is better."

The long study I read about this  issue is now dated.  The source was Ford
Motor motor design research and it only applied to water cooled spark ignition
motors (not my favorites).   The final result, considering all the trade-offs,
seemed to be that 190 - 195 F. degrees was the most desirable operating
temperature design goal for these auto engines.   As I recall, BSFC efficiency
was slightly better than at lower temperatures.  Oil service life, assuming
normal use thermal cycle periods, was MUCH better with high temperature
thermostats than with lower controlled temperatures.   Apparently at lower
temperatures, the typical run time for each cycle must be much longer to
evaporate combustion condensates from the oil if it's cooled a lot. Sorry this
isn't super simple, but I'm only giving a micro view of their exhaustive test.

Converting your 80 and 86 degree centigrade values to 176 and 187 Fahrenheit
will be helpful in trying to apply this information.  But please note that
these thermostat values don't give a one to one relationship to engine
operating temperature.  That part depends on a lot of other factors.  But for
concerns of overheating, at 200 degrees, both your 176 and 187 degree
thermostat options should be fully open, so the lower temperature thermostat
shouldn't be able to provide more cooling in that circumstance.  It should
only open earlier.

Cooler is not better.  Also, if the Vanagon cooling systems were more closely
coupled and had more capacity, I believe the 86 degree C thermostat would
always be better for your gas engine.  But that "if" factor just isn't true of
Vanagons.

So there's a comment with perspective, but without a settled conclusion for
your vehicle.  As usual, I could be wrong.
John