High Oil Temp 912ULS

James Stricker wrote:

Sean Griffin wrote:

James - Most if not all light aircraft engine gauges are at best indicators. That is, as long as they remain fairly consistent in their readings, all is usually well.

The pilot should monitor for any change, not so much for the numbers.

If your oil pressure remains acceptable, then it is likely your temperature gauge is reading high (ie above actual temperature).

Sean - What you say is true, however my real problem is that I installed a new exhaust system and oil temps are now 30F higher on hot days.  I have Dynon D180 EMS and I think indicated temps are pretty close to actual.  

My real concern is if 250F is acceptable operating temp for Rotax 912 using Mobil 4T 10W40 Full Synthetic Oil.  I have been searching internet (I know – not good idea) and see that full synthetic oils can operate near 300F.  I spoke with tech support at Mobil and they said they don’t publish a max operating temp, only that their product is good for high-revving motorcycles and high temperatures.  Tech support said they would investigate and get back to me in a few days.  Hopefully they will, but could be ploy like telling kids “later for sure…”

Senders/sensors can & do degrade & fail.

You have not answered the question on oil pressure.

No matter what max temperature the maker of the oil claims - internal combustion engines are designed to run within fairly close temperature ranges. All sorts of components are impacted by running above the recommended temperature.

If an engine that is maintaining its oil at  120C,(148F) in cruise, there is a problem - I like to see oil temps, in cruise, below 100C (38F)

I don'r see reduction in oil pressure with temp increase.  I will start collecting data on oil temp, oil pressure, and OAT.  

See chart below....

Food for thought.

This may be normal for your RV12.

I did read on the RV12 forum that others have the same issue of being 230F in cruise. After all these years seems like Vans has had higher engine temps under the cowl than others. They have the highest VR failure rate over any other MFG I have seen, but they're the only ones I know that park the VR within inches of the #4 exhaust pipe.

Something else that may help is to modify your cowl. Some have opened the cowl openings and or added a 2.5" angled down and rearward oriented flap on the bottom of the cowl that helps increase the air flowing through the cowl.

VR (Voltage Regulator?) - I agree with Roger - should be kept as far away from heat source as practical. Can be located on the cockpit side of the firewall 

Roger -

I am interested in your opinion on this....  d06902.pdf

Section 6 states...

6) General engine operation requirements and operating tips 

1.     Keep the engine oil temperature below 120 °C (250 °F) over most of the operating period. 

2.     Always insure that the oil type used is adequate for climatic conditions and peak engine operating temperatures. If operational oil temperatures exceed 120 °C (250 °F), use of a mineral or petroleum based oil is not recommended. 

3.     For turbocharged engines ensure an adequate running cool-down period to prevent deposits by coking of oil. 

4.     When operating with unleaded fuels or MOGAS and when engine oil temperatures often exceed 120 °C (250 °F) use of a high quality full synthetic oil is recommended.

5.     To avoid formation of condensation water in the engine oil, the oil temperature must rise at least once every operational day to at least 100 °C (212 °F). 

6.     Avoid extended use of carburetor air pre-heating when safe and reasonable. 

7.     Automotive fuels have seasonal blends and MUST be used in the correct season. Failure to do so can cause hard starting or serious issues like vapor lock. 

8.     Depending on the type of fuel used, operating conditions, and the demands of the engine mis- sion profile it may be necessary to increase the frequency of oil changes to avoid the excessive build up of lead and other residues in the engine oil. Always adjust the engine oil change intervals to avoid excessive build up of sludge in the engine oil.