90 F150 4x4 bought new from factory order.
pennz 10-40 for 1K then 3K more to break it in, then M1 10-30/15-50 mix to get to appx 10-40, then at 30K ams 10-40, in the mid 100'sI would experiment with pennz 10-30 syn or qs 10-30 syn, or valvoline...never was satisfied, went back to amsoil until 200ish then been on castrol 10-40 syn. 5k avg change intervals. towing nearly every weekend heavy things. many many highway miles. been inside at appx 205ishK to fix a bad intake gasket - carmel on the block, but the shiny stuff thats supposed to be shiny is. runs appx 52-53psi at highway speed. idles 20-25 when smoking hot.
super engine cooling so never overheated. tranny is original too - changes every 30K up till 180K then every 20K - currently have 217K and change on it - using dexron/mercon - mostly wolfs head. inside of tranny is spotless, never any matter in the pan. and yes, I have a tapped converter so I get all 12qts out.
ams 75-90 in the front axle - never opened it. had amsoil 75-90 in the rear till I found out it helps wipe out trac-loc plates, was running straight gl5 90W from ford with lim slip modifier, until 175K the pinion bearing started going so I had the axle rebuilt, running dino 75-90 with a fresh set of plates.
All in all, I perhaps have less than the usual amount of ford rear main leakage. I use a qt every 2K roughly. I can tell the motor has lost a step power wise, but I think it has more to do with injectors giving up the ghost, im showing signs of being a bit lean on the plugs. 331inch stroker motor still sits in the garage awaiting assembly.