I have seen 260 F. many times, and I consider that
normal during climb
and taxi. I also use Mobil One Synthetic oil, to tolerate the heat.
During cruise it will stabilize at 220F.
You need to get the oil above 220 F, to evaporate the moisture anyway.
The "standard"
(closest we have to one) for measuring oil temp is to measure it as it returns
to the engine, after the cooler. According to Racing Beat, this temp
should never exceed 210 F. Lot's of folks have exceeded this for short
periods, up to 240 F or so, and have had no problems, but it's not something
you really want to keep doing.
As I understand it, the
issue is not the breakdown of the oil, but the melting of the
rotor bearings.
Hum-m. I was under the impression
that the limiting factor side seal O-rings.
I’ve had the oil temp (after
cooler) up to 220 -225 a few times for very short periods on the ground. With
no effective air flow through the cooler, the before-cooler temp was only 3-4
degrees higher. It’s a different issue when running at high power
where before-cooler temps may be 30-50 degrees higher.
Al