What oil to run depends on the engine. If you've got a pre '97 engine run nothing thinner than a 10w30, you will see lower oil pressure at operating temps with a thin oil. The oil also dissapates heat. If your running an oil cooler with a high velocity fan on it go ahead and run the thin stuff as it will never get hot enough to thin out. Also remember as the engine spins it wears out, meaning that the clearances get bigger needing a thicker oil to fill and properly lubricate. And to the guy running 12k between oil changes, get another vehicle and change your oil every 3k and then send the oils off to be tested, then post the results. I am also insulted that you would ruin a Ford with a foriegn engine.

 

When I got my 01 van I called the dealer about the 5w-20 oil. I asked if I had to us it or could I use 10w-30? He told me that it would be fine. I called a second dealer and got the same ok. This guy also told me that the reason for the 5w-20 was for fuel milage rating.