I use to use it on a carbon build up prone M5 and the results were noticeable. Now i use BG and techron as a preventive.
As old guy said, use it prior to an oil change is a good idea.

 

See the attachment shows the 40k miles service.

 

This shows the fuel addtive as 'additional dealer service', so it's not part of any Porsche recommended service.

I'm a DYI kind of guy. I'm getting the impression that most here are not.. $1800 for an oil change, air filter, cabin filter, wiper blade, bottle of Techron and a minor visual inspection and test drive. I'll do it on mine for $150.

No fuel additive will do squat for intake valves on a DI engine, since the fuel is injected in the cylinder.

 

True, but the valves shouldn't get as dirty in the first place. At least the stem side. In any case it should help clean the injectors themselves regardless of where they're located, which is the main point of the additive supposedly. I agree $1800 for an oil and filter(s) change plus a bottle of tech is asinine. I'm fine with "paying to play" and want dealer stamps in a higher end car like this to the greatest extent possible, but I'll probably line item veto a few bogus price gouging things here or there.

 

There is plenty of detergent in gasoline already to keep the injector itself clean.

As for 'dealer stamps', all I can say is good grief.

 

FYI, I didn't have the dealrship do the service. I went to an Indy and it was $700. That also included plugs, which i have heard were worth the money to pay someone to do it. Otherwise I would have DIY'ed it

 

In some parts of the world "dealer stamps" are still considered as being priceless.

Somewhat ironic given the fact that most Indy shops take more pride, are more thorough and flexible in their troubleshooting and general repairs.