For a while, i have been having trouble with my chevy trucks with them running cool. I replace the thermostat and it fixes it for a small amount of time like 6 months or something. I have been fighting this issue in my 1500 for a while. Well today i drove my wifes blazer today and the temp only went up too one click above 155 which would be about 168 on the gauge and the OP was slightly higher at idle so i believe it was actually running cool. I called GM and one of the mechanics told me my issues were most likely caused by cheap thermostats that have weaker springs that wear quickly. He recommended going to Napa and getting the premium superstat by stant. I did so and it definitely feel better than the cheap ones i have been using. I put it in an went for a drive and it did fix the issue. Im just wondering if others have run into this with cheap Tstats including the failsafe brand which really was not all the cheap.