Palut,
I have been investigating this for a while now. I have not found a gauge mfg. that provides a drain plug sender. I have seen oil filter adapters with a port for a temp gauge but am wary of anything that may interrupt oil flow. As well from what I've been able to judge the oil pan is the most accurate place to take a temp reading. I was trying to see if I could make my own oil drain plug with a 1/8" npt fitting, problem is there may not be enough metal in the plug to allow for a hole drilled big enough to accept the sender. As well these plugs tend to be very hard steel so drilling is difficult. You would need a drill press. I have found a NAPA part # BK704-1909 drain plug which seems to solve the problem, at least for my needs. I have a 92 Montero that I want to keep track of oil temp. NAPA makes this plug with a pre-drilled 1/8"npt hole in it. AutoMeter has a sender that is 5/16" dia.x 1/2" long with a 1/8" npt x 12mm fitting that sticks above the sender by about 1". The threaded bolt on top will take a spade connector so that when you change your oil you just disconnect the connector. This is an electric gauge. The wrench needed to turn the new plug is a 13/16". I drilled the center larger by going with larger and larger drills at low speed and using lubricant. This plug is very hard. The hole I was able to drill was 11/32" and there seems to be enough metal left so the threads on the drain plug would not strip or collapse. If you go this route, especially with a Honda, you will need to see how far below the pan the plug extends. You don't want to drive over a speed bump and tear it off. My Montero has plenty of ground clearance with splash pans for protection. Hope this helps, maybe someone else here can also help.
