The funny thing is that no where in my owner's manual or Warranty & Customer Information manual is any kind of maintenance discussed. Kind of weird isn't it.
I had to discover the oil & filter change intervals from my Bentley Service Manual after I about fell down when the mechanic at my local Porsche dealership started telling me that the Boxster was one of the least maintenance intensive vehicles Porsche produces (e.g. oil changes at 15,000 miles, oil & filter changes every 30,000 miles, etc.).
So I checked the Bentley manual and
Porsche Boxster (986) FAQ (this was in 2009, so the link may not still be active) and both confirmed what the mechanic was stating.
My 1999 Boxster has over 233,000 miles and I change the oil & filter every 10,000 miles.
You cannot beat that good old German engineering:-)
It would be nice if Porsche had installed an oil useful life sensor like Chevorlet started doing back in 1997 on the Corvette (it provides a estimate of how much useful life your oil has based on a whole lot of parameters such as miles driven, total rpms and operating cycles since the last oil change). That is American engineering!