* Engine size: One-ton trucks in 1985 offered a range of V8 engines, with larger engines resulting in significantly lower fuel economy. A smaller V8 might get slightly better mileage than a larger one.
* Transmission: Automatic transmissions generally had slightly lower fuel economy than manual transmissions.
* Axle ratio: Lower numerical axle ratios (e.g., 3.54) are geared for better fuel economy on the highway, while higher numerical ratios (e.g., 4.10) are geared for more towing power, sacrificing fuel economy.
* Vehicle condition: Proper maintenance (tuned engine, correct tire pressure) impacts fuel efficiency.
* Driving habits: Aggressive acceleration and high speeds drastically reduce fuel economy.
* Payload and towing: Hauling heavy loads or towing a trailer dramatically decreases gas mileage.
Realistically, you'd be lucky to see more than 10-12 miles per gallon (mpg) in combined city/highway driving with a typical 1985 Dodge one-ton truck, and it could be considerably lower (8 mpg or less) depending on the factors listed above. Expect even lower mpg when towing or carrying heavy loads.
To find a more precise estimate, you'd need to know the specific engine size and transmission type of the truck in question. Even then, it's just an estimate based on averages; actual mileage will vary.
