Stop in for a cup of coffee

Well, people in general tend to disapprove of random strangers walking up to them telling them they're wrong. Even if they are.
Yeah.. I tried doing that to a guy filling up his literally brand new Ford f350 diesel from the E85 pump..... I was filling my trucks, watched him pull straight from the dealer into the station.......tried to tell him. He got pissy said that diesel can use any fuels.......