I run Mobil 1 5W30 and a K&N filter and time change it every 4 mos. (3500-4000 miles)
It has always tested well within normal specs even with the abuse I put it through on a daily basis.
The wife's car gets 3 mos time changes (~6k miles) and tests even better than mine.
Like I said the Duratec, high rpm's, and myself
are quite punishing on oil. Hence one of the reasons I so highly recommend synthetic oil for it's added protection and performance.
