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 |
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