I run 10w30 full synthetic oil from Canadian tire in mine with a Ford filter. Also, have a JLT passenger side oil catch can.
Here is a picture of the oil:
10w30.jpg
Steve just try using the heavier weight oil as a fix, it may work.
Don’t believe I have any issues yet and I plan to “enjoy” my 5.0 very much on May 13th at TMP. So the only tick I am worried about is coming from the stopwatch as I need to get better lap times. LOL