hard times at the track

Well I changed out the T-stat for a 180 degree one. The one that was in there looked brand new but I could not figure out which one it was:shrug: I just bought one from Pep Boys it was only like $7 is it bad to buy a cheap one because it was the only one they had? I also was wondering if it was bad to go from 93 octane to a tank of 87 octane then back to 93 octane?