Don't know about your engine, but on my Lycoming O-360-A4A the vernatherm is
an oil cooler bypass valve and when the oil is hot it closes to force all of
the oil through the oil cooler. If it doesn't seat properly, oil leaks past
the oil cooler and the oil gets too hot, not too cold.

--
Best Regards,
Mike
http://photoshow.comcast.net/mikenoel
"Peter R." wrote in message
...
A few weeks ago while flying through -17 degree C air aloft, I spotted what
appeared to be really a low oil temperature indication of the
turbo-normalized, IO-520 engine in my V35. For a few moments, the oil
temperature was around 125 degrees F.

When I landed I contacted my mechanic, who verbalized that he suspected
the
oil thermostat (the valve that controls the oil flow into the oil cooler)
was bad. In his experience, he stated that the oil temperature should be
around 180 degrees F.

After removing and inspecting this thermostat, he concluded that the valve
was not seating properly and that most likely allowed oil into the cooler,
despite the lower oil temperature. Thus, I authorized the replacement of
it (it was under warranty).

These days and with a new thermostat installed, I am only seeing oil
temperatures of no higher than 155-160 degrees F while flying through air
of +1 to +5 degrees C. Does this still seem low?

BTW, I did share this observation with my mechanic and he called Tornado
Alley (manufacturers of the turbo-normalized system). TA was not alarmed
with the 155 degree F oil temperature.

For some additional information, the oil cooler is located on the top of
the firewall, directly behind the engine, rather than in the front.

--
Peter