Oil consumtion can be caused by a bad turbo. what happens is that the brass bushings inside of it wear out and eventually making the turbo spool jump inside of it and make the seals go bad. then oil consumtion starts. just cuz its burning all the oil it doesnt mean that its going to smoke. some times they dont. believe me it happened to me. you will start to feel the truck running rough and as you accelerate it starts to smoke. dont worry you wont make it far if your already low on oil. there is turbo rebuild kits. thats if your exhust and compressor wheels are still good! but you still have to take your air to air or charge air cooler off to clean. because that stuff is just nasty knowing that your air to air is full of all 3 gallons of oil.