Regular or Premium

Regular or Premium
When the family car developed a slight knock, the wife asked her husband if he had bought regular or premium gas, but he couldn’t remember.
“You probably got the cheaper gas,” she said. “That could account for the engine running so rough.”
“No, the gas wasn’t cheaper!” he replied indignantly.
“Well, how much did it cost?” asked the wife.
“It cost the same as always,” said the husband. “I bought the usual ten dollars worth.”