I just replaced mine recently at around 98K miles on the M113 engine. It makes teh engine run a few degrees warmer in the cold weather, but I can't say whether it's significant. Before it was always spot on the 80C hash mark, and now it steadies out with the needle covering the top loop of the "8". That should be 87 degrees, but I would think 87 is a bit higher on the gage, given that the next hash mark should be 100.

The only reason I bothered to change it was that I was seeing a lot of creamy oil goop under the oil filler cap, so I figured warmer oil may help to burn off any condensation. But I can't say yet if these few degrees make a noticeable difference.