Low Cruise Oil Temps

First...no panic..

with an OAT barely above freezing that temp is not too bad.

There are a few things...

1) You can as many do in colder climates and during winter, put a little aluminum tape over a portion (say 20%) of the oil cooler. This will increase temps at all times, in full summer you may have to remove it if temps get too hot.

2) Check whether you have an oil thermostat, many do not as it is not  essential. this will help but mainly they assist in warming up not peak temps from 65c they are normally fully open.

3) We do oil changes much more regularly than cars and they have little problems with corrosion.

4) Unless you are getting creamy foam under the oil cap or down the oil tank overflow line then there is little to no moisture in the oil.

5) Now the controversial statement.

IMO Rotax is wrong you do not need 100 degrees C to remove water from oil.

Water vapour pressure is related to temperature and relative humidity.

Water will move from a liquid so long as the vapour pressure at that temp is higher than the vapour pressure in the surrounds. You DO NOT need to heat a damp towel to 212 degrees f to dry it, at room temp it will slowly dry out ! The higher the temp  the faster the process but it is not binary, ie at 165 F it works too it is just faster at 200 or 220 etc. Rotax has "simplified" the physics for us dumb pilots, and really I believe the getting to 100C should be a "recommendation"

So I would not panic if you do not meet the "magical number"

Glenn

That all makes sense. I have seen the whitish foam in the oil, but that was on the very very first engine start and taxi tests when I was doing exclusively taxiing and not flying. Ever since it has been clean. 

I cant help but be confused as to the "normal operating range" setup on the oil temp gauge on the Garmin. Are others just cruising below the green arc on the gauge all the time like I am?

I do not know, it is very easy to set the Garmin arcs but they should be at Rotax specs.

Try some tape to put it up a bit and will help with any moisture and with peace of mind.

I seem to be about 90 c at cruise and full power climb hit around 100, depending on the day....so just in the green. Same on both my planes (870 and 500 hr) and our club planes that we swap the engines a 2100 hr (TBO +5%) are the same. After 2100 hr they still have original compression etc and look very good inside.