I have a 94 Suburban with 84K original miles.I bought this truck off in My grandfather in Illinois then drove it to Florida when I get there I check the oil and discovered that there was no oil. it was full before I left on the trip there is never any blue smoke the oil pressure gauge never dipped and the temp never went up. so I did a full oil change and drove the truck for about three months never losing any oil. When I move back to Illinois i made sure to check the oil often I was losing 2qts every 400-500 miles again no smoke when I got about 2 hours from my home in IL I seen the 1st and ONLY puff of smoke i pulled over and the oil was gone empty. I parked the truck and got in my other car went to my dads house to get his truck to tow it back before I loaded it I check the oil and after sitting for 4 hours the oil was full truck is still my daily and uses very little oil as long as I don't do long highway trips so again NO BLUE SMOKE OTHER THEN THE 1 TIME SO IF UR ANSWER IS IT'S BURNING OIL THAT'S NOT THE PROBLEM my best guess is the heads are very dirty and when the motor gets super hot it is getting stuck in the heads this is the only reason I can think that the oil would return after truck cools