Thanks for all the input. To respond to some of your questions/comments: I have read "Bob the Oil Guy" column in the past, so I am somewhat educated on oil grades, viscosities, etc. I previously was running a motorcraft filter, which I believe is pretty good quality, so I don't think that was causing a drain back condition.

I ended up putting in castrol 10w-40 with a wix filter. Drove it around town for the day and everything seems fine. I know that the stock gauges are not that great, but I'm getting identical oil pressure readings as I was with the 20-50, so I would assume the pressure is about the same.

I will report back after I've put some miles on the truck.