I'm running a Toyota OEM Tstat with the overheat pellet cut. Running a regular Stant OEM replacment Cap. 50/50 Prestone coolant. new fan clutch. Pulled the radiator and had a Radiator shop rod/flush it out. I like 190 tstats for milage. cooler ones won't keep your engine from overheating. Tstats regulate the COLDEST your engine can run.