Looks like according to the thread at TDi club:
Modified Thermostat for higher MPG's... - Page 31 - TDIClub Forums
"Modified Thermostat for higher MPG's" page 31 post 451 tells about a guy who used a mark 2 high temperature thermostat in his ALH TDI, and seems to be getting an increase in MPG's. Then again, you could just make one of my "Hybrid" 205 Deg F units:
I am seeing a 3-4 MPG increase over my previous T-stat that only reached 186 Deg F.
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