[Walt Fricke]

The stock hard lines are closer to AN12 than to AN16. A hair larger than the -12s. Not enough to matter.

Where the AN16 is useful is in a full on race 911 with a 4 or 5 gallon oil tank in the smuggler's box area. The cooler side of things has plenty of pressure pushing the oil along. But some gravity and the suction of the oil pump are much lower pressure, so there is something to easing the passage of the oil from tank to pump. I thought I was tip top when I put in a -16 line instead of the -12 one (which had worked just fine) on my modified 911, but immediately saw a car with -20. My car came with -10 up and -12 back.

In terms of oiling, what counts on a stock 911 is having the oil level in the tank always high enough to supply the pump's demands. Larger lines may cut down some on the parasitic power lost in driving the scavenge side of the pump, but that's probably trivial.

I suggest using -12. You can purchase an adapter which will allow you to connect a -12 hose end fitting to the metric fittings Porsche uses.