Have been monitoring this site for some time now and have done numerous searches to help me decide. Have the '03 F-150 4x4 with the 5.4. Engine has 8k on it. First 2 changes were with the motorcraft 5w20. Currently have the Havoline 10w-30 synthetic in. Want to run the full synthetic Mobil 1. Will be changing oil between 3-5k. No more than 5K. Summers in Detroit area usually see 90f+ in the thick of summer and close to 0 deg.f in dead of winter. I am at 50% highway and 50% city. That highway number is soon to drop as I have acquired a "beater" car for work commutes ( 83 miles round trip). I have narrowed my choices down to M1 10w-30, 0w-30, and 0w-40. I will not run the 20 weight. I have seen the numbers so far and am impressed, however, I do not feel comfortable running it. Sorry so long and thank you in advance.