a little fyi they will not void the warranty. here is the trick that the dealer uses i know i work for one.

step1 drain the fuel out useing a hose siphon out as much as you can try to get the fuel guage to read E. change the fuel filter add stanidyne diesel conditioner to the fuel tank and add diesel to system 5 gallons. prime the system and then start let it idle for 10 min and then get it to a fueling station and fill it up again this time with diesel . it should be ok. if it is chattering or has no power then you may have a problem. but make sure that you get out as much as you can. make sure that you have some cans to put the contaminated fuel in then you have some fuel for you lawn mower