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watch how much longer it takes to get an oil pressure indication after a very cold start
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Something wrong here. Oil pressure should rise within 30 secs.
The concern in cold weather is excessive pressure as warned by Lycoming, wait for longer time for oil to warm at low rpm's (lean engine to avoid plug fouling). At power checks watch the oil pressure when increasing throttle - do not allow it into the red sector. Excessive pressure will cause damage.
Also in car, drive at low rpm until warm.