This is just my opinion but I think that putting the oil temp sender in a "tee" fitting at the same port that the oil pressure switch is, just wrong. Here's why I think this. There is no oil flow out thru that "Tee" fitting . There's oil pressure there but not oil flow so It seems to me that the temp's that the oil temp. sender is reading is heat transfer from the aluminum crankcase thru the brass "Tee" fitting to the sender.
A couple years ago I posted the results from having 6 different senders indicating the temp's of the same oil flowing all thru the system. The location with the biggest lag in reading the temp. was from the Oil pressure port. A couple of times that temp was still showing the temp. climbing when all the others were dropping in temp. If you have a type 3 crankcase (which I did) with the dipstick port blocked off with a little aluminum plate.....that was the best all round place to measure from. Next was out in the external cooler plumbing.
The real surprise was the stock oil cooler in the fan shroud. I installed temp senders both on the inlet and outlet side of the cooler adaptor. (photo below) The surprise was that that cooler only dropped the oil temp 4 degrees F !! No matter what temp's I got, 4 degrees was it ! The amazing part of that is that cooler handles hundreds of gallons of oil per minute and still is able to drop the temp 4 degrees plus pretty much keep a lid on an acceptable oil temp.
