Gasoline in Diesel Fuel Mistake Hack. ---This morning after making a delivery, I went to the fuel pump to fill up. I absent mindedly started the gasoline pump running and realized 1 gallon in. I immediately stopped the pump and filled up the rest with diesel and drove to our office. Around 30 gal. diesel to 1 gal. gas ratio. After calling an old seasoned mechanic, he said to put in a quart of Automatic Transmission Fluid (ATF). He said it is actually good on traditional diesels for lubrication. We have put in the ATF and will see how this goes. Just passing on the hack (Hopefully it works). (Contact your personal professionals before trying anything drastic. Obviously much more ie. 2 gal. and above might require draining the mixed fuel.)