Oil

I have a 1989 Custom Cruiser, a Oldsmobile. It Has a 5.0L 307 V-8 with 146,000 miles. It runs silent, it sounds new no knocks, pings, pops, nothing. But it does burn through allot of oil, like 4 quarts in 400 miles. So if you have any idea of what it might be, oh when I put oil in I see white smoke coming from the oil spout, and I have very light white exhaust. So any information would be nice. Oh yeah it also keeps running after I turn it off, like in National Lampoons Family Vacation, just kind of chugs and knocks and then off. But not all the time.