At 07:47 PM 5/24/2012, Rocket J Squirrel wrote:
>But I read here, frequently, that it's not a good idea. (This does
>beg the question why VW made the lower-temp part.)

Did they?  Or is it an aftermarket part?  According to Etka the
thermostat is the same for all WBX, whether in USA or Germany, and
they do not show an alternate in either list.  Also that thermostat
is unique to the WBX in both markets.  P/n is 025 121 113 F.

The engine will use some increment of additional fuel and/or produce
less power when using a cooler-than-stock thermostat.  See
http://www.importtuner.com/tech/impp_1001_colder_thermostat_increase_power/
(as a side note, Smokey Yunick thought that we'd one day be running
ceramic engines that operated at red heat for increased
efficiency).  Also note that the OE thermostat in the link above
starts to open 2C higher than our stock thermostats; although the
colder one they used in the test was *very* cold (71C).

Yours,
David