Wow, I've got a potentionally expensive problem. Changed out the oil im my 80 recently about 2k miles ago. Used castrol High Milage Oil 10w-30 with a FRAM filter, switching to 20004 on next change so dont flame me. Right now about 11 quarts have gone into the 80. Started with about 9qts to start. Dont know if this is normal but right now the oil dipstick is on Low and the oil light is coming on. Inside the truck the oil meter is at the 2nd hash from the top which is "normal" from the manuel. Here are some pics of the underside, tell me what you think.