912ULS min Run-up temp issue

the issue with cold oil in a Rotax 912 is more that it is too thick when cold and you get cavitation. Rotax is the only engine i have worked on that they suck / draw the oil through a long line and the oil cooler. you may note that when cold  you can drop the rpm and the oil pressure goes up. As it is an Aviation engine I run Rotax oils only. The cavitation can cause lifters to draw air  and lead to valve failure. I have had Rotax motors fail due to simple things saving a few cents  here and there. Valve failures destroying a motor at 600 hrs  take your time save your engine and life  a few min is not worth your engine or life.   

An oil thermostat would make quite a difference.

I would really consider installing a Tanis engine pre-heater. It's important and really helps when people live in cold country. It will help save the engine too from hard cold starts. I have installed a number of the Tanis engine heaters and is well worth the money if you live and fly in cold country.Watch the video.

https://www.rotax-owner.com/en/videos-topmenu/product-reviews/149-tanis

To clarify a few items:

I do have a Tanis Heater and heat oil to about 50 degrees F prior to Start.

Oil pressure is fairly consistent on start and cruise between 38 and 41 pig.

Again, Oil intake grill is taped off about 3/4 with Duct Tape.

Almost a half hour in mid 30's to 40 degree F seems rediculous just to get above 100 degrees F Oil Temp.

I am really wondering about the accuracy of your temperature sensor and/or gauge.