When I was in High School, I worked as a petroleum transfer engineer. There used to be an old man who drove a Mercedes that would stop in once a week or so for a fill up.
The first time he did so, I filled his tank, and told him how much he owed.
He asked "Did you run it over the side?"
"No,sir."
"Then it ain't filled up. Run it over the side."
"Yes, sir."
From then on, I filled his tank and then ran it over. He felt like it would would give him a little extra mileage. I don't know if in reality it actually did, but it was his car.
I figure loading my pistol and topping it off might give me the extra mileage I need. Makes me feel a tad better. In reality, that one round probably means very little, but it doesn't hurt.
