I switched over to Mobil 1 5-30 around 6-8 months ago and today I noticed when I checked my oil I was nearly a quart low! I am at about the 4200 mile mark on this oil change with a WIX filter. I have no leaks at all, nor is is blowing smoke. Everything else seems fine....runs fine...etc. Anyone have any imput? I have roughly 40K on the truck now.