Royal Purple has acceptable zinc content and is synthetic... 20W50 and you're good to go... Plus it's a cool purple color.
Now to add to the discussion, We for the most part use our cars differently than most of the people considered in that article. Not many of us daily drive these cars. At that point you have to consider time and not miles as the benchmark. I use spring and fall as change points.
A friend of mine, who is a 914 guy who lurks here and has a high performance shop that works on BMW, Porsche, Audi, etc. differed with the owners manual on my wife's Audi A4 2T. I think her manual said 10K miles but Ron said he uses a benchmark of 1000 miles per quart capacity. That cut the factory interval in half I think.