Wow I thought I was the only one with this problem. I'm in No cal where it is in the 40s at night. My thermostat hits 1/4 after 10 minutes on city streets, but stays just above or at C on the freeway. Based on the discussion here it seems there is no way to adjust it, only replace it. BTW do you have to drain the coolant to replace the T-stat? I'm about to have a coolant flush done tomorrow.

At the same time have any of you had your radiator leak between the top plastic housing and the metal? I've had that happen twice and I wonder if they deliberately did this to the stat to prevent the radiator from leaking.