Oil Temps

[netconn]

My M5-235 must run the coldest oil temps in the lower 48... In the winter the oil runs about 148 degs, OAT about 36 degs. In the summer the oil runs about 168 degs, OAT 100 degs. I changed the vernatherm made no difference. I have a JPI 830 monitor and the factory gauge, both read about the same. Engine power is usually 20 MAP & 2100 RPM cruise. When I park the plane I open the oil filler to let the steam out...
What oil temps do others see during the year?

[Kirk]

I also have an M5-235C. Both the previous O540-J1A5D and current O540-B4B5 run very cool with the standard oil cooler. I talked with a lot of Maule experienced mechanics and pilots who all agreed it is a common issue.

Based upon their advice, I installed the Maule winter baffle year ‘round. It only covers about an inch of the oil cooler and worked pretty well in the summer. In winter I added a strip of 2” foil tape.

With the new engine and overhauled oil cooler I leave the 2” foil on year ‘round and the oil regulates right at 180 degrees like it should.

[Andy Young]

I have found the same to be true with my IO-540-W1A5D. In the winter the main air supply to the oil cooler is about 7/8 covered, and the smaller supply that points at the top tank of the cooler is completely covered. Even then, I often cannot get to 180°. In the summer, the main supply is usually about half covered, and the smaller one is covered or uncovered depending on air temp. That allows me to keep the oil at about 180°-190°. I’m in Alaska, so summer temps tend to be in the 50°-75° range.