Compression testing question.
I got to talking to a buddy at work today about what the correct way to check compression is. I've always pulled all the plugs and then checked one cylinder at a time. He say's you can check one at a time and the readings will be the same as if you pull all the plugs. So, who's wrong? I realize that for a ring test you don't want to pull them all again, and it seems to me that the more you have to turn over (say 7 other plugged cylinders), the lower the psi would be. I could be wrong, just curious though.
Thanks in advance, Chet.