Robert Overby (Overby's Inc.) is also a high end shop here in Jacksonville, as well as high end sales, and he also recommends Pennzoil full synthetic (Platinum). Robert is a multiple SCCA National Champion in E-Production - Porsche Speedster.
On my last DD change I went with Pennzoil's Hyper-Clean full synthetic, Ultra, and the Mazda Turbo used a bit less of it than the regular Pennzoil Platinum.
The 135k miles CX7 was using about 1.5 quarts of Mobile One (5/30-high mile formula), used about half that of Pennzoil Platinum (10/30) and now has used about 1/2 quart of the Ultra (5/30). These are all on 5k mile intervals. It's due for another change this week, so I will be using the same clean formula Pennzoil.
I was expecting the 5/30 Ultra to have the same consumption as 5/30 Mobile One, thinking the differnce was molecular weight, but I was wrong, or at least mistaken!
If I did the turbo cool down idle time routine, it would probably burn less, but too bad, time is money and I am terribly impatient!
Brumos still uses the Porsche Spec Moblie One, but Overby and others have told me the Mobile One you and I can buy, over the counter, is nowhere near the same spec as the Porsche dealer gets - through Porsche parts division, not the oil dealer.