IMO, cold is where it matters most (for me anyway). you may not get smoke but thats when you will see maximum blowby, so if you have a lot, cold starts will be a PITA. many people can get a read with a poor mans test, the oil cap upside down on the fill tube. if it blows off (not vibrates off) then you might get an actual copression test.I dont get any smoke when it's cold. Whats the difference?