I think the oil moves too fast through the turbo to be use it for the turbo temp. I have a oil temp guage in the port on the filter housing, works pretty well, the oil temp stays within a 15 degree range regardless of load or ambient temp, once warmed up, the range is about 220 to 235, I have not seen it go any higher than that, hardest I have pushed it was a 6 mile hill in 3rd at 2500 rpm, 90 degrees out, pulling 10k lbs, maybe it goes higher with more of a load.