Does the thermostat open gradually and vary the opening depending on temperature or is it just fully open or closed. Reason I ask is my temp gauge has been showing strange readings over the last couple of weeks, for the 35 months Iíve owned the car the gauge has risen to 82/83 within 2/3 miles from cold and stayed there, the only exception being heavy traffic in warm weather when itís risen to 90. Now itís struggling to get to 80 (still within the usual 2/3 miles) then drops down to 70/75, creeps up to almost 80 and then seems to slowly fluctuate between the two extremes. Also, on a 250 mile trip last week the gauge sat at 80 the whole way with one exception where it rose to it's normal reading for a very brief period then back to 80 again. All very perplexing.
Iím pretty sure itís the stat, just looking for an other opinion.