flexfuel

My friend put about 15 gal of flexfuel in my 2006 Duramax, thinking it was B20 diesel.  It was run about 1 mile before clouds of white smoke poured out.  I drained it as best I could without dropping tank, refilled with diesel.  It sputtered for about 10 miles and then seems OK.  Did it seriously hurt the engine?  

Theoretically, yes it could have damaged the hi pressure related components such as the cp3 and ofcourse the injectors. Only time will tell the severity of the damage. Depending how diluted the e85 was with the diesel already in the tank. The ethanol will burn hotter and faster than diesel if it was of high concentration. If that is the case than its possible to have sustained piston or valve damage. But in most accidental gasoline cases I have repaired, so long as mileage was low, u should b ok.  
Rich
04.5 GMC 3500HD CC/LB LLY: EFI, 75%inj,120% CP3, FASS 150, 71.5mm w/HX40, PPE  manifolds/upipes/rails, studded everything, stage 1 heads, Snow stg 3 Meth, Carillo rods, Mahle pistons, Haisley Intercooler, LBZ MP and bridge, Stage V Allsion w/co pilot and 5 Star, 4.10s much more...
06 GMC 2500HD CC/SB LBZ: 68mm Garret w/DP billet wheel, Suncoast Gmax 6 w/billet shafts, Raptor RP100, PPE manifolds,85% CP3, much more...
2011 3500HD H&S, Snow stage 3, much more...

Yes, you damaged the injection system. Expect a very large repair bill soon.  

nice posts,thanks for the info...  
allen