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The approach I take is a yearly oil service, everything else is as per the recommendations in the service book (I live in EU). Whether this makes a difference, I cannot say. One would need to run an extensive trial with multiple cars over an extended period of time, but then what are your analysis endpoints. Porsche has likely done several accelerated tests and simulations during development to arrive at these recommendations. US is geographically very diverse and to account for all possible variables weather wise, once a year oil change interval covers everyone. I worry more about crappy roads than anything else with my 911.
Thank you everyone for your input. As some were asking, here is the info I was basing my original question on. I was just curious why there would be a difference in the recommendation provided by Porsche between USA vs Europe.
All of the Maintenance Books I've looked at (for Swiss-based 997.2s) have been serviced every 2 years (see attached photo as an example)
Below is the email response I received from Porsche Center in Geneva, Switzerland, where I am based and shopping for a 997.2. I was asking to get some rough estimates for service costs, and the sentence highlighted in yellow says "the maintenance plan is carried out every 2 years or every 30,000 km, so I can confirm that there is no annual oil change in the maintenance plan".