I do (after a bit of research) believe Doc's filters are rebranded PTC Filters.

http://www.ptcauto.com/fuel-filters

I know from after chatting with a Ebay Jobber of the PTC filters - There are Many Fleet operations all over the country that run these filters in their 6.7L.

Prices from this Jobber is a bit cheaper (w/Free Shipping) then Doc's advertised prices.

Not saying they are of the Highest Quality - but who is to say the OEM filter are at that level.

Note: OFF Topic & I apologize

I have found that in my area Oil/Fuel/Air Filter prices have gone up ridiculously (Maybe due to they are all made in China)

I have created a stock pile of all 3 (Hording) if ya will (Via/Amazon & Ebay - Amazon is now getting hit with alot of Out of Stocks) - just in case quality becomes an issue - I know HDEO at the local walmart is almost to the point of Empty Shelves!

I have about 3yrs worth of filters in reserve & trying to stock pile at least 3 OCI of HDEO - Mainly TRIAX Supreme ESP 5W-40 & 15W-40 & ATF.