Ford recommends the engine oil be changed at 15000km or 12 months, which ever comes first.
I did some research and found out that synthetic oils are capable of that sort of service intervals, but Ford does not use a full synthetic oil.
The engine oil in my Territory has been analysed at about 3000km & 5000km (company paid for it), and the results of the last test came back with a caution.
I replaced the oil with a full synthetic POA (PolyAlphaOlefin) 5w30 and instantly noticed an improvement in engine response & economy.
I will change the oil when the Terri has done 15000km, which will be 10000km for the oil, & then change it at every 15000km.
Later I will use an Ester based engine oil 0w20 which is manufactured using Canola oil, I have used it in my previous vehicle (turbo charged).
Posted the oil analysis results from my Terri here Oil change
And there is an discussion on oils here what lubricant gets ur motor goin
If the dealer is using a full synthetic engine oil, change it every 15,000km, if they can't tell you, bring your own oil.
The Porsche Cayenne oil change recommendation is 30,000km or 2 years, which ever comes first and only Mobil 1 0w40 is recommended.
Here is some oil info, probably bore you but knowledge is everything; http://www.240sx.org/faq/articles/oil.htm
When looking for an oil, go by the European rating system ACEA http://www.acea.be/ASB/ASBv1_1.nsf
it is tougher than the American API rating http://api-ec.api.org/AdvancedSearch.cfm