High Oil Temp 912ULS

I did Annual Condition Insp last month and found a crack in the muffler.  I advertised and found a like new (70TT) early SN complete exhaust system identical to my original RV-12 exhaust system.  So, both exhaust systems are the same.  I looked today and clearance between back of oil cooler and front of muffler is very close.  I suspect my original system may have had more clearance but now have no way of telling for sure.  Data point from this mornings flight.... 75F OAT and oil at 238F in cruise.

238F in cruise is high. I don't see that temp unless it's summer on climb out and it cruise at 5200 +rpm it's only about 215F - 220F on a much hotter day than 75F.

Are all other temps, pressures and other gauge parameters normal except oil?

With your oil temps in cruise I'd be looking for a cause. Maybe a reduced radius hose, bad thermostat if you have one (just had this happen in a Flight Design CTLS), maybe something in the oil cooler and needs flushing (flush cooler backwards of the normal flow), did you clean the oil tank and reverse the plate on the bottom? Swap the #2 CHT wire for the oil temp and see if each still read the same. These two temp senders are the same.   

Right... the original exhaust system I had for 750TT and this serviceable exhaust (70TT) are same vintage sourced from Van's Aircraft as part of original kit procurement.  I'm investigating any difference in mounting, etc.    But, question remains.... is 250F acceptable oil temp for Rotax 912ULS when operating with Full Synthetic Mobil 4T 10W40?  250F is about midway in yellow arc for Dynon D180 with Van's preset limits for oil temp. 

James,

The answer to your question is not in the Rotax Operators manual? My 912UL states 260F is the maximum allowed and normal range is 190-230F.  I run around 220F at 5,000 rpm cruise in the Summer and around 190F in the Winter.

Jim Isaacs wrote:

James,

The answer to your question is not in the Rotax Operators manual? My 912UL states 260F is the maximum allowed and normal range is 190-230F.  I run around 220F at 5,000 rpm cruise in the Summer and around 190F in the Winter.

Then maybe the next logical question would be.... is maximum 260F based on petroleum oil?  Perhaps Full Synthetic Oil can tolerate higher sustained temp?