chevron 20w50, changed out every 3000 miles, sometimes less... 110*F dusty summers.
motorcraft FL1-a filter, changed at time of oil.

i've heard from several folks smarter than I, that what oil you run isn't as important as keeping it clean and fresh... so a good filter and frequent changes are more paramount than $5quarts of super juice.
Having said that, I run super juice in my Mustang.