[SD987]

Well, here is a challenge. Run the oil for 20K MILES and then take a small sample and send it to Blackstone labs for analysis. I think this is a $15 charge or so.

Then report back to us. I think you will be literally amazed at what our dear Porsche engineers have been recommending.

To save you some trouble, using M1 0W-40 oil, the UOA I have seen indicate that this oil is SHOT at about 10K miles tops.

That is NOT true of Red Line oil which is likely good for 15K.

..umm, what exactly would running your test indicate? In order to be of any value, sampling would have to be done at intervals (say, every 5k), along the way. No doubt the oil degrades but is the degradation at 20k so much more versus 15k, or 10k or 5k to justify an earlier interval? At what point does the oil degradation justify changing it? I'm guessing both Porsche and the engine oil companies have run just a couple of these tests. Since car companies often provide guidelines to protect the consumer from his/her self I'd say the 20k interval is actually understated.

And your response doesn't answer the question posed by z12358. If a shorter interval was required, why wouldn't Porsche simply make that the interval? There's nothing to gain with a shorter interval, no prestige is bestowed on a marque for having the longest oil change interval, nor is there "shame" in a shorter interval. There's only the downside of increased warranty claims, as noted by z. And there's only downside in a long interval for a company trying to sell oil. Yes, M1 wants to be known as a "long lasting oil", but that reputation could be garnered with a 10k interval.

I know you enjoy bashing Porsche on maintenance/reliability but there's little credibility in a Porsche/Oil conspiracy. If there is a conspiracy, Mercedes (my SLK interval is 13k) must be "in on it" too, then.