I just changed the oil out in my cheapie air compressor, which based on the amount of metal visible in the oil, i should have done years ago. anyway, it is winter and it always has a hard time starting when it gets down around 20°F or lower so i put in Non Detergent SAE10W oil. I also bought some "synthetic blend" of unknown weight that says it is supposed to be better for extreme temperatures (high and low), but opted for the 10w because i figured a flush with a short OCI would be a good idea. so the question is: what's the upper temperature range at which i should change out the 10W? 50°F? 60°F no owner's manual to be found, and can't find much on the net otherwise. i will say this, the 10W makes the compressor much easier to fire up in the cold! thanks in advance!