Checked the oil before flight a little more than 4.5 quarts where it should be on this plane. I have a hard time getting the fill cap on as it is in an awkward place at a weird angle. I think I must have gotten it tightened cockeyed and not really screwed down tight. Anyway about an hour flight land and wife unit says is that mud on the strut? where did that come from? I said no that is oil. CRAP! At some point the cap came unscrewed. Made a mess all down the side and bottom of the plane took an hour and half+ to clean. Thankfully only lost about 1/2-3/4 of a quart. Never noticed any pressure or temperature problems and I check fairly frequently. Never had any on the windscreen which might have at least let me know. Lesson learned check and double check to make sure the cap is screwed on and threaded on right.