Originally posted by tcodi
the sender is the drain plug, that's what the gauge company offered.
I do not have an oil cooler.

The oil definitely does take a long time to heat up, much longer than the water, but even after about an hour drive it was below 140. It used to run hotter when I was just test running in my garage. It also seemed to cool down as I drove at speed for a while with lots of air flow.
Perhaps it is reading slightly lower than it really is, but I think it may be better for my engine to run 5W-20 or so just for the winter.
Do you guys agree?
No, I don't agree, assuming that your gauges are mounted and working properly and your water is running 160 to 180 degrees then it sounds to me your oil temp is probably what it should be. I've never heard of anybody trying to increase the oil temp without increasing the water temp. I left home this morning it was 10 degrees and in a few miles the water temp. was 200 and if I have had a gauge in the oil it would have been around 180. I use 10w40 motor oil, and I had 50 lbs. of oil pressure. you don't need a 5w20 in 40 degree weather. I always used an oil gauge to make sure the oil didn't get to hot, I wouldn't think to cold would be a problem in 40 degree temp. its a wonder you have heat as cold as you're running the motor. heat the water and the oil will take care of itself.