I also read in this forum about how Mercedes even OK'd diluting diesel with gas in ultra cold climates. Try a search to find.
My Dad used to have a VW diesel Rabbit. He was very smart and often preoccupied. He so frequently filled the car with gasoline, that the local gas station wouldn't even charge him to empty the tank. They thought it was very funny how often it happened.
Like the stories from the VW Beetle years ago, we'd borrow his car and would put a few gallons of diesel in it without him knowing it. He checked his mileage religiously. He regularly reported increased mileage: 35, 40, 45, 50! 60 MPG. We finally told him at 85 MPG. You know we were a bit sorry after all of it, for he was really disappointed he wasn’t actually getting 85 MPG.
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)