It's not just the individual readings that are important, the variation between cylinders too. Ideally you don't want more than 10% variation. Of course lots of factors determine the ideal.
I remember way back when I checked a straight 6 vauxhall running on 5. Zero compression on one cylinder and running as rough as anything. Head off suspecting a burnt valve and found no piston or rod fitted and a jubilee clip covering the crank journal oilway. No wonder it was running rough!
Did the owner lust after a 5 Cyl Audi perhaps ?
