Whats all the hullaballoo about M1 in the Northstar??? I used Mobil 1 from day one in my 91 Continental (Bought it with 12K mileage). This is the worst car I have ever owned in 43 years of driving. Replaced every front and rear brake, hydraulics, motor mts, air bags, alternators, any many other components!, at least twice!! The motor has just turned 180K +. No smoke, runs like a top, uses about a quart of oil every 1600 miles. I changed the oil every 6K (As I feel oils are better these days then when I was hotrodding back in the 50's and 60's when I used to do the every 3K routine myself). I believe my 99 Caddy warranty book recommends a regular oil change every 7500 miles. I own a 99 Seville which I absolutely love. It just turned 48K. I have followed the 6K M1 oil change on the Caddie. I do not have one oil spot on garage floor. She doesn't smoke. She goes about 1500 miles before needing a quart of oil. Should I be worried!!!