Yep, this subject almost gets emotional at times.

I've been using Motorcraft Semi Syn in my '31 (as well as the wife's car and my DD truck). Usually been either 10W-30 or 15W-40 for the '31 as I feel that the 5W-20 is a little light for heavier valve springs and roller rockers. I can't find anything but the 5w-20 locally unless I go to their diesel specific oil. Is there any advantage to my using this Motorcraft Diesel specific oil? Disadvantages? Or should I just switch to Valvoline which is my other long time favorite. Not interested in Amsoil or Royal Purple (way too expensive to use in that car and the amount driven). I have used Mobil 1 and do like it, but for a car only driven a couple thousand miles, probably isn't cost effective either. Then there are the racing oils like Joe Gibbs and Brad Penn and no sellers any where locally according to their web sites, nor do I think that I need these oils for my kind of driving(Oh yeah, I wont EVER use Castrol again).

Mostly I'm interested in comments of what others use and why