I have used, Motorcraft(10w30,15w40) Rotella(10w30,not impressed,15w40) Royal Purple 15w40, Amsoil 15w40, 5w30HDD, Texaco Ursa 15w40, Delvac1 5w40(3 times), Delo 5w40.
I did UOA's on each except the Ams 15w40, MC 10w30, RT 10w30.
Best mileage increase Amsoil 5w30 HDD
Worst wear numbers of the...