I bought this 01 6L new, at 74000 KM's it all of a sudden started drinking up to 2L of oil a day,it also had a loud knock,not the typical chevy tick,service manager said " oh that ticking is normal" they told me it needed an upgraded pcv valve and the knocking was from carbon build up on the pistons...changed out the pcv and dumped some chemical in to clean the carbon, all at my cost,brought it home drove 160 KM's down 2 liters of oil and sounds like a deisel again,I don't know who the knothead at GM is who designed these motors with the loose tolerances,to get longer engine life,but he should be shot...back to the dealer tommorow!!! you'de think by spending that kind of money on these things they'd last more than 70000KM's