2001 SLS Oil Consumption

I have a 2001 Northstar engine that uses oil. It has 103K and runs good. I keep the oil changed and engine tuned. About every 300 mi. I have to add a qt. of 10/30 Valvoline synthetic blend oil. I've tried several WOTs, no leaks on garage floor, and no smoke from exhaust. Does not run hot. I'm at a loss as to what the problem might be since it slowly started using this much oil? Any ideas? Thanks ellis479

Well, if you look at history of this engine this has been a chronic complaint, google Northstar oil consumption problems, plenty of info, barring leaks the engine must come apart!!