Hello, I have a 1966 Valiant 200 with a slant-6 225, 1 barrel carb, and 3-speed automatic transmission. What kind of mileage should I be getting? When I bought the car, I was under the impression it would be somewhere around 18-22 for an average. As it is, I have been calculating 10-11. Why am I getting such poor mileage? It just doesn't make sense to me.