First time I've done it, everything was within spec (only about 1000 miles on the Mobil 1 5W30 over 2 years) except for one thing: Lead, which was high at 62 instead of 0. Their speculation was that the previous owner may have used an octane booster and it hasn't worked its way through the system yet. Not sure why someone would use an octane booster, as mine is just the plain jane XK8, but who knows. They did say it could be bearing wear, but since no other metals were present it was unlikely.
I also got the TBN analysts and they also told me I could probably increase the oil change interval to double the mileage, but I'm not comfortable waiting that long (4 years?!!) and honestly wasn't all that comfortable waiting 2 years for a change. I guess I should drive the car more to hopefully work through the lead,
Fun data to have, I guess.

Norm

 

When I worked at the dealer and the new car warranty included scheduled maintenance, we would change the oil every 10K miles OR once every 12 months.(whatever was sooner)

 

I do the oil changes myself, so other than oil, filter, and drain plug, not much cost involved. The town recycling center takes used oil so disposal is easy too.