That's a lot of oil gone. Is it leaking out of the rocker cover and burning on the exhaust? Three quarts burned while driving would be a real stinker at that.
There is some oil that has come out below the valve cover.
Also, I usually only see visible smoke coming out of the tailpipe on startup and when I rev the engine. Not when I am cruising or idling. The smoke is whitish greyish.
