I have used M-1 5w20 in all 5 of my previous foci. I use M-1 5w30 in my 04 Yukon Denali started when she had over 160K on it not one problem. I plan on using M-1 in my ST after brake in. I seem to side with Tom on this.
2013 Focus ST-3, Tuxedo Black " Pugsley" my 6th Focus
2002 USACi SQ world champion builder/owner/competitor
Drag racing is for fast cars, Autocrossing is for fast drivers