I would like to know why the next writing is a joke.
My Mom loves to tell the story about one of her first dates with my Dad. One night they took a drive on a quiet country lane. As they got to an isolated spot, far from home, the car rolled to a stop. "Out of gas," my Dad said. My Mom opened her purse and pulled out a bottle.
Wow!" said my Dad, "A bottle, what is it?" "Gasoline." was the reply
Not a teacher.
The subtext here is that the boy was trying a ploy "I ran out of gas" in order to park with the girl in a isolated place in order to try to make sexual advances on her.
The girl was having no part of it.
"Running out of gas" on a date is a very old cliche. It supposedly was a ploy for the man (the driver, and owner of the car) to spend some time with his date in a dark, isolated place. Just the two of them, in his car. Eventually (particularly in the 1940s and 1950s) "we ran out of gas" became sort of a code phrase for a person to use to indicate that they'd spent part of the evening kissing and "making out."
Janet: "You got home very late last night. How was your date with Brad?"
Alice: (blushing demurely) "Oh, we ran out of gas."
Janet now understands that after dinner and a movie, Alice and Brad spent the rest of their date smooching and necking in Brad's car.
A very savvy girl (like your mom) might anticipate such a tactic from her date and bring a container of gasoline with her.
I should have pointed out that in my original reply, when I said that the man "conveniently" ran out of gas, that I didn't mean it literally. I meant, as the others have said, that the man was pretending to run out of gas in order to get the girl to an isolated spot. A rather nasty trick!
Note: in BrE, that would be "run out of petrol".
But noticing your remark and rereading your original reply I realize it would be better if you had written the word conviniently inside quotation marks rather than brackets. Italics would also do it.
At the first the 'joke' didn't sound so funny, as emsr2d2 pointed out.
But when I stop to think about the poor savy lady always walking around with a bottle of gas, always 'ready' for any date, I do find myself laughing about the situation. Just think about it guys!