This is the unit many of us installed on the early RV-12's Solid unit that works flawlessly. Fails safe to allow oil to engine all the time. A real asset to cold weather flying. I still needed to block off 3/4 of the oil cooler on the RV-12 under 20F, and fly comfortably at -8F.
I think John Bender or Marty Santic gets the credit for finding this unit, but I had added a similar design to my 912s ultra lights 5 years earlier.

Seriously, a thermostat on the oil is a good idea. We went with the 209F temp. Worked great. IMHO.
http://www.mcp.com.au/thermostat/