Mobil1 does not have a 20W-50 weight. They do have 0W-20, 0W-30, 0W-40,5W-30 10W-30 and 15W-50. I use 5W-30 in my windsor with lots of pressure. Use the lightest
oil you can that gives you the pressure you need. Use a quality filter (Mobil1, Wix, AC, etc.). Mobil1 info at
www.mobil1.com .
While we have a guage to measure pressure, we do not have a guage to measure flow. If the
oil you're using is too thick the flow may suffer while the extra pressure is just pushing
oil out the bypass.
Bob