I bought a 98 GMC Sierra with a 5.7L v8 a couple months ago. It has 150k miles on it - and from what I can tell it doesn't go through any oil - at least not in the 1500 miles since I had the oil changed. When I got the truck I drove it for a few weeks - in the extreme cold (as cold as -15 degrees F) and it ran great - no noises or problems. Since I had the oil changed it seems to have a deep "knock" that is pretty quiet - but noticable for the first minute or so at cold startup. I plan to change the oil again soon to try to aleviate this problem - and I bought a Purolator Pure One filter and planned to run Mobile 1 5w30 to see if it makes a difference. I am a big fan of Mobile 1 ever since living in ND during the extremely cold winter of 1996-1997 when the temps reached as low as -49 F! Any thoughts?