Maybe a stupid question, but I haven't seen the answer anywhere, at least nowhere unambiguous. My engine is an O-290-D, how warm does it need to be before I take off? I've been waiting until the needle at lest starts moving off the peg, which is 90°F. No big deal in the summer, but the past few times I've flown it's quite awhile that I'm sitting in the runup area. In flight the oil temp seems to run around 100-110° over ambient, so today (55F) it was running a bit over 150. Too cold? Should I block off part of the oil cooler? Most of what I've read about "cold weather operations" talks about far lower temperatures (10-20F) than I'll ever be willing to fly in with an open cockpit.