Right Austin a typo sorry - 15W 50 it is because we can buy it here.
However Porsche recommends 15W 40 and not the 15W 50 that we buy locally in the US - far more 928's in the ROW than here.
I checked with Royal Purple and 15W 40 is readily available and with the levels of ZZDP we are looking for to suit our older cars.
Not a lot of difference between 15W 40 & 15W 50 just depends on the cars operating conditions.
I would hesitate at recommending 15w-40 as an acceptable viscosity for our engines.
You need to be carefull about recommendations unless you define the operating parameters of the vehicle.
