The oil they tested in the article isn't the quart bottles that you find on store shelves, it's the bulk stuff from large tanks and 55-gallon drums found at quick oil changes, dealerships, service stations, mechanic shops, etc.
The stuff on the shelves almost uniformly meet the API specs that are stated on the label. It's rare for them to test and find any that don't meet the standards, at least from any brand name you've ever heard of.
But the stuff in the large tanks and 55-gallon drums are rarely branded. And even when the barrels are branded, when those barrels run dry they are usually just re-filled with bulk oil from an oil truck rather than changing out with a new barrel.
Look at all the different brands and types of oil (10W-30, 14W-45, etc). Quick-change and other places would need dozens of different barrels to mirror that, even if they just used a single brand of oil. Instead, most places have 3 barrels, some even have as many as 5. My Dodge dealer at home, for example, has 5 barrels (3 dino, 2 synthetic) next to their oil change pit, and they all say Mobil 1 on them, but none of the oil in those barrels is actually Mobile 1 - it's bulk oil, in different weights, out of an oil tanker truck. If you go there and want your oil changed, and ask for API spec oil, or ask for a specific brand or type, they won't use the oil in the drums, they will use cases of quart bottles from NAPA down the street, and you'll pay more than the $19.95 or whatever it is for the oil change. If you take your Sprinter there, they will use Mobil 1 out of the quart bottles, and overcharge you appropriately for it.
If you buy your own oil off the shelves and change it yourself, you are pretty much assured of getting quality oil, but if you take it to an oil change place (including the big truck oil change places), not so much.
At the API's
Motor Oil Matters page you can search for oil change places, and distributors who distribute API certified oil to those places.
