Ok i get really confused when reading all these posts on different weight oils. Im not that good at understanding it all. Right now in my 97 f150 4.6 v8 i have 5w30 m1 full syn with the motorcraft filter. I used to use 10w30 m1 full syn. But read somewhere to try a thinner oil to save on mpg. But that hasn't done squat. I do mostly city driving 75% 25% highway. Im coming up on my next oil change and want to know what I should use? Im going to get this oil analyzed to see whats going on. I've got 104k on my truck right now.