Hi,
well another oil thread.
bought the car new in 2003. Only use it in the summer season. In the first years i didn't know about any engine problems and the car was driven 20.000 Km per year, and was allways inspected by official Porsche dealers. They also did the oil change. Allways with Mobil 1 0W 40.
In the last 6 years i drove no more than 2.500 - 4.500 Km per year. And i began to do repair stuff myself, because of the relation between Porsche workshop prices and the car value. Since then i change the engine oil and filter at every season ending in october.
When i began to do the stuff myself i recognized a little oil film between engine and transmission after the car standing in the garage from october to april and decided to use a thicker oil. Now using a half snythetic 5 W40 oil. Also put in a fluid that softens gum sealings. No more leaking since than.
I think a 0 viscosity isn't good if the car isn't a daily driver. The oil is to thin and the car will start to leak when it's older. For seasonal used cars i would recommend a 5, or 10 W oil (if you don't live in a region where it doesn't allways snow).
ZN may be an aspect. But there are also other additives that help the engine.
Calcium (Cn) improves engine cleaning and improves the soil carrying capacity
Magnesium (Mg) improves corossion protection, thermal stability, the soil carrying capacity
Boron (B) improves the engine cleanliness
Zinc (Zn) improves the wear protection
Phosphor (P) improves the EP characteristics - improves corrosion protection, reduces friction
Barium (Ba) can improve the EP characteristics; mostly use in ATF to change the coefficient of friction
Sulfur (S) only in mineral oils. Wear and corrosion protection. Mostly combined with Calcium and Zink.
So if you use a full synthetic oil Zink is an important part. Whereas if you use a half synthtic oil you also have sulfur as a wear protector.
There are also other aspects like acids if you drive only very short distances, or if you never change oil and filter.
For the Boxster engine the most engine fails are caused by a failing IMS. And that is because the bearing seal fails. There are a lot of theories out there why this happens. I don't think because of the lack of Zn. I think the seal is weakend by the lack of softener. A problem every plastic, or rubber seal has when time goes by. Maybe new oil is tess agressive to the seal. But i don't know if that is a main aspect.
Also allways keep in mind that a manufacturer recommendation for an oil costs the manufacturer a lot of money.
Regards
Markus