Well, I had recently finished my RX rinse phase and had decided to use Pennzoil 5w-20 GRP III In my 2001 Screw due to extended warranty (Ford Spec) concerns. I figured if I was gonna use thin 20 wt, I should at least go to "synthetic" for the extra protection. I decided to go buy another batch for my upcoming Oil change, and Guess what....I couldn't find it anywhere in town Not even at the Wal-Mart I had originally purchased it from. I could find plenty of the 5w-30 and 10w-30, but no 5w-20. Now I live in a town of about 60,000 and have no less than about 10 large Auto parts stores which include Auto Zones and Oreilly Auto parts. So I went ahead and put M1 0w-20 in it. I hope I can still find that when I do my next oil change(it dissapeared from Wal-Mart for a couple months) I'm sure it is a better oil anyway Anyway, I just felt a need to vent my frustration at stores that flip-flop on their availability of certain oils. On a side note, should I run a short interval to rinse the Pennzoil out, or will the residue mix with the M1 with no concerns?