For some reason my truck is loosein oil. It dosent smoke and it dosent leak, except for the rear main seal witch dosent leak hardly at all ( I'm talking a little wetness, no dripping) I am getting a gas smell which I already know shes running a little rich, but where is the oil going??? I have had to put a quart in my rig in the past month. I'm thinking of going from 10w30 to 10w40... Its strange, if its burnin oil seems like it would smoke?? BTW, My truck is a 87 gmc sierra classic 4x4 w/ a rebuilt 350 TBI and a 700r4, 208 tansfercase and a 8" superlift suspension lift w/ 35x12.5's on 15x12" rims.