I'm thinking about buying a 1993 Ford F350 crew cab 7.3L diesel for $5,500, look likes it in excellent condition. Would be used as my main car, and often used for long-distance trips, with people in the cab, and tents, food, etc in the bed. However, I don't want to buy something with totally shitty gas mileage. What should I expect from it? 350, 7.3L diesel.