Last fall, I purchased a Crown Victoria Sport, and of course Ford recommends 5W-20 only. I asked the Ford service manager and heard the same lie as every other customer. "The engines are much tighter now and need the thinner oil" and that noise is "normal". Being a Cop and spending my youth in Missouri, I just assume people lie to me. My Victoria has had a 3/4-second knock when starting after sitting for 8 hours in mild weather, but not on cold mornings. I asked our fleet manager who services all 65 of our Police Vics, and he said we use 10W-30 regardless of what Ford says and that there have not been any design or tolerance changes in the Ford 4.6 since 1993. I tried Mobile 1, 5W-30 at 2000 miles and drained it after 60 miles because it made the start-up noise worse. I replaced the M1 with Motorcraft 5W-20 and it was "normal" again. Last week, I found my old favorite, Chevron Supreme 10W-30 which recently has been hard to find in San Antonio. Using the same proven FL820, and six quarts of Chevron, made the engine so quiet, I can't believe it's the same car. Now my short question after such a long lead in. Are the M1 and the Motorcraft 5W-20 not sticking to the journals and the "old dino" chevron stickier?