Fundamentally warranty coverage and warranty repair approval comes down to a marketing decision. Ford is the largest seller and GM was just coming out of bankruptcy when the CP4 pumps came on the scene--both their marketing departments were doing the math and making a decision. I have read of (supposedly) actual cases over on www.thedieselstop.com (Ford forum) where the Ma and Pa station had algae and water in their fuel and another where the lazy delivery truck driver didn't adequately flush the ethanol out of the truck tank before loading diesel. Doesn't matter--water, DEF, gasoline, or ethanol in the fuel is going to blow the pump. From memory the NHSTA numbers were .06%, 6 in 10,000--and Ford repaired some of those. Yes, it would suck if it happened to you. But, I give every fuel stop the 10 second fresh fuel evaluation--does it look high volume and how desperate am I for fuel? And, I get a receipt for every tank of fuel so I could go back on station insurance if there is a problem. Also, some have gotten the repair paid for by comprehensive vehicle insurance when warranty was denied.