I think I use Core Temps
I dont quite remember whats it called when I used to check my temps while I OC'ed my CPU. I also used Everest to compare the 2 to see if they match.
I open up Core Temps, and leave it running while running the game. I game for like 10 minutes or so. I quit the game, and it shows whats the max temp the CPU has gotten over the time of gaming.