Originally posted by rfrazier
I my opinion, 5 gallons of gas mixed in with 25 gallons of diesel is not going to help it much but should not be a problem of significant consequence. That is about 20% mix. Rather than drain it out and throw it away; I would mix in as much diesel as possible along with a hefty dose of a good fuel additive. Siphon back out 20 gallons or so of the mixed fuel into some Walmart yellow fuel cans and top off with more diesel. (now you are down to about 11% mix) Then mix in one of the 5 gallon containers of the mixed fuel back in with each subsequent fill up.
Yes, the optimum fix is to drain the entire tank and system if you have run gas mix through it. Just keep in mind, it used to be a fairly common practice to mix a little gas in with diesel to prevent it from gelling. (not that I recommend this or think that it is a wise practice)
Your choice, I can definitely see the arguement that it is not worth chancing your $5,000 option Cummins engine and warranty. On the other hand I would hate to waste nearly $50 worth of fuel. You can put the fuel cans to good use later. I usually keep 6 cans of diesel that I fill when I go to the Flying J as I am so far from it. They have a big price discount so I use the 6 yellow fuel cans to make the trip worth while.