/6 Mileage ?
When they were new, I could understand the mileage. I ran across an old add that claimed the then new '75 Toyota Corrola was advertised @ 38 mpg's. Today, few cars top that.
As time goes on, the car becomes worn and can no longer produce the power it used to even though it may perform strongly. My previous slant six gave absoulutely poor mileage to the point that I don't mind driving and paying for the big blocks consumption. (LOL, 3 times the HP doesn't hurt ethier.)