Oil at room temperature (75 degrees) flows well enought to lubricate the engine. I always wait until I reach at least 75 degrees before a get the engine RPMs above 1000.
Probably over conservative, but I use 100 f minimum oil temp for run up and 125 for take off.
Cheers,
db
One problem I have had with all these numbers is winter flying without preheat. You wouldn't be flying much.
Even on a day with temps in the 30's, it would take an hour of ground ops to get OT up to 125F on the 7A with the air flow to the cooler shut off. Piper recommends a baffle plate over the cooler with temps below 30 and even at that, they have to say it is is ok to fly if pressure is normal.
I read one engine guru recommending 140F minimum for take off. I sat in a run up pad one cold day for 45 minutes just to prove the recommendation was BS.
No question, preheat is good for any engine and I use it. You taxi out with 100+ and that's a good feeling. But these engines are not at all wimpish. If preheat was not used and the gage is off the peg, the engine is ok for flight.
What a cold start does for engine life is another issue. Mike Bush at OSH made a pretty good case for preheat in that he calculated there is much engine wear when starting a cold cold weather without it. Waiting for a minimum temperature for take off is not going to undo the damage already done by starting that cold cold engine without preheat.
Lots of different opinions can be expressed, but I agree with David's study of the manufacturer's data. I am generally comfortable at 75 degrees, as I know that the gauge is well off the peg and I can trust that it hasn't just flipped a bit.
Paul
Under the Operating Conditions section in the Lycoming O-360 Operator's Manual there is a little note..
* - Engine oil temperature should not be below 140F (60C) during continous operation.
So, does "continous operation" include take-off?
David D (or anybody else). Do you recall what Mr. Bush has said about the desired RPM (lowest possible or higher than normal) after start of a cold engine? I have read his articles and he seems very knowledgable, but I don't recall a comment on this? Thanks. Dave
I'm with Dave D. above. The start is what kills and that has nothing to do with oil temp since it's just sitting in the sump. What remains on internal services is what's there when you start. Running to a higher temp doesn't ameliorate start wear.
So everyone must be concerned with circulation. Well, what of viscosity effects? That hasn't been mentioned. And just where are you measuring the oil temp? At what temperature you like is the temperature what it should be by some undefined standard.
Got pressure? Oil's o.k. Thinner helps circulation, sure, but I like seeing 200+ CHTs before full power, oil is what it is.
John Siebold