There appears to be a lot of concern about engine oil consumption and something called PISTON SLAP on the newest GM V8 and V6 engines. My tow vehicle 2001 2500 HD Chevrolet with an 8.1 Liter Engine is experiencing a loud knocking sound that started off as a light tapping that went away when the engine warmed up. It has now progreesed to a loud hammering that doesn't go away after the engine warms up. I'm also using about 1 Qt of oil per 2000 miles when not towing. There is a site that has a lot of information about this problem at http://www.gmpistonslap.cjb.net if anybody has more interest. Is anyone else on this forum experiencing any of these problems?