[s_morrison57]

Conv. oil will start to break down when it is heat cycled, I'm talking driving the car not sitting in a heated garage. After it is heat cycled the first time a 1 year and/or milage time frame should apply.
I've done testing on small air cooled engines at work and everytime the engine that had more oil changes lasted longer - everytime! I had a new 87 Civic and I got free oil from work, by the time that car had 12K on it I had probably changed the oil 20 times, I gave that car away when it had 230K on it, the engine had never been touched and was doing changes at 3K by then. I never had to check the oil between changes as it was down maybe 1/6th of a quart and the oil was still brown on the stick. IMO you can never go wrong with frequent oil changes. My buddy has a 09 Cayman and the factory says 18K klm's between changes - to me thats dumb, but then Porsche does want to sell the parts or rebuild your engine for you, he does his 2/year , I do my 930 every year and put less than 1500 miles on it. Its up to you, pay a little bit now or a heck of a lot later.
Finn