I hate to drag up old stuff, but North America is the only place that I've seen where 5W-20 is called for by Ford. (Note, the SVT Zetec is supposed to use 5W-30.) Anywhere in Europe and in Australia and New Zealand they call for 5W-30 or even 10W-40. It isn't a "closer tolerance" issue, it's fleet average fuel economy regs. These "North American" engines don't have different build tolerances than those used anywhere else. What got my attention was that Nissan (I've owned one for 3 yrs.) for example, does essentially the same thing. In NA they recommend 5W-30 as the "preferred" oil, but you can use 10W-30 or 10W-40 if the temp. is over 0 deg. F. In Europe, Nissan recommends 5W-20 ONLY for temps. UNDER +14 deg. F and it is NOT recommended for "sustained high speed driving", and even the 5W-30 is only recommended for temps. below 59 deg. F. Above -4 deg. F any 10W or 15W-XX oil can be used, and above +14 deg. F any 20W-XX oil can be used. Now here's a hint........Nissan also states that...... "5W-30 oil will positively improve fuel economy". The Nissan VQ 30 engine in my car is built to the same tolerances irrespective of where it is used, so why the difference in oil recommendations? It goes back to the NA fuel economy deal again. This Nissan info came to mind when I bought my Focus and of course was confronted with Ford here recommending the 5W-20. My Nissan engine has the standard basic plain bearings, has chain (oil jet lubed) driven DOH cams with direct acting cam followers, a crankshaft driven oil pump, and a pressure regulated lubrication system just like my Duratec in the Focus, and with engineering principles being what they are, all the bearing clearance tolerances have to be within a certain range or limit to "physically work". My Nissan engine's piston clearance limit is .0004 to .0013" and I don't think you can get any tighter than that. And I'm aware of the principle of leakage, flow and cooling. Because I have a thing for (a fear of low) oil pressure, a decade or so ago I did some "real (my) world" oil testing with my '93 GM "L" body car, that had a 0 - 80 p.s.i. oil pressure gauge. Over a period of about two years and several oil changes I "experimented" with mineral oils of different oil viscosities, and one synthetic (Castrol Syntec). At that time the oil that gave me the highest oil pressure readings both at hot idle and at highway cruise was a 15W-40 (Castrol RX Super). With this oil the oil pressure was about 60 - 65 psi at highway rpm and it never went below 30 psi at idle. This oil of course "starts life" as a SAE 15 oil, so no surprise there. This had been my regular oil that I had used in this GM car and a VW Rabbit for a number of years. It of course does not meet the present API specs. I tried the Castrol Syntec 20W-50 and much to my surprise it had almost the identical results as the RX Super. I tried a 10W-30 (Castrol Canada XLR, now GTX) which yielded about 55 psi at cruise and about 25 psi min. at idle. 5W-30 was just starting to be recommended and available, so I gave it a shot (I think it was Castrol) and it made me nervous because at idle the oil pressure dropped to just under 20 and at cruise it barely got to 50 psi. That has always stuck with me, and I do understand that oils have improved in the last decade, and Ford has their spec. for the 5W-20, but I believe that to protect an engine under severe conditions you can't beat viscosity (actual) and the higher viscosity oils seem to have the better "high temp. shear" ratings. Also with manual tranny cars, where you invariably load the engine (pop the clutch) sometimes almost at "stall" rpm with minimum oil pressure, I want as high an idle oil pressure as possible to protect the main bearings etc. So, for me, where I live, both my cars are getting 10W-30 and because I don't feel like screwing with success, where except for my first car, every car that I've owned has never used/burned any oil to speak of and I've had anywhere from 110,000 to 325,000 miles on them when I got rid of them, and I refuse to use an oil that starts out as a SAE 5. BUT, with the average Focus owner ("the daily driver"), still under warranty, and because most are not going to hang onto their cars for as long as I tend to do, then using the recommended oil is probably the way to go.