Oil Change Interval for Synthetics

In my case I don't think Ford offers the 4.6L V8 or the FL820S filter in europe. (not that some don't get there anyway)

That said, each model should be checked to make sure it really is the same filter being used in europe. If it is, that would be sticking with OEM filters. (wouldn't trust another brand not to have shot for the US reccomended service interval) I would be comfortable with such a long interval in that case.

That's a big part of it. Large engines such as those in over-the-road trucks keep the same fill oil for unbelievably long times- many 10s of thousands of miles. But there are two big differences between them and passenger cars:

1) they have multi-stage filtration systems with much larger and more effective filters which are changed more often than the oil itself, and 2) they have oil capacities measured in tens of gallons, which means that the oil passes through the engine many fewer times per thousand miles than is the case in an automobile engine that only holds maybe 6 quarts.

Darn right. A three dollar investment for a three thousand dollar engine job is a no brainer