On June 7th, 2012, we bought diesel fuel from the I-90 Travel Plaza (Shell) in Mitchell, SD.  About 270 miles further west, the "REDUCING ENGINE POWER" message appeared on the dashboard display and the engine went to idle rpms immediately.  The AC Delco filter on our 2009 GMC 3500 Duramax had passed the water and particulates contaminated fuel to the injection system, damaging the injectors and fuel pressure regulator.  No warning messages or lights were triggered until the REDUCING ENGINE POWER message was displayed seconds before we lost power. The WIF (water in fuel) warning did not appear at any time.  With only 32,700 miles on the truck, GMC denied our claim without analyzing the fuel, fuel filter or water sensing system.
Our cost: $9,142.12
($517.50 in taxes on the fuel related charges included.)
($465.60 in unrelated scheduled maintenance, $298.82
     in campground and car rental fees & taxes excluded.)  

Bottom Line: Don’t trust the stock GM fuel filtering system, the  water-in-fuel sensor, the "CHANGE FUEL FILTER" sensor or your GM warranty.

If you have had a similar experience, please contact me at bennf@nsfd.net.  A class action suit against the fuel station and/or GMC may be possible.