My Girlfriends 1990 2500's 350 has started to blow bluish white smoke. Tell tell signs of rings going bad, I guess after 175,000 miles it was bound to happen. She used 1 quart of oil this month, started to visibly smoke. I have been told that running thicker oil can prolong engine life for a while, till january would be very nice If i could. She us currently running 10W-30, Can i run SAE 40 or 15W-40 diesel engine oil and slow the burning? I have heard from a friend that ran thick oil in an aging Chevy 4.3 V6 and prolonged its life for several months. What would be the best weight to run? 15W-40? SEA 40?