* Engine size: The Silverado came with a wide range of engine options in 1986, from smaller inline-6s to large V8s. A smaller engine will naturally get better gas mileage than a larger one.
* Transmission: Automatic transmissions generally consume slightly more fuel than manual transmissions.
* Vehicle condition: Proper maintenance (tune-ups, properly inflated tires, etc.) significantly impacts fuel economy. A poorly maintained truck will get considerably worse gas mileage.
* Driving habits: Aggressive driving (rapid acceleration and braking) reduces fuel efficiency.
* Payload and towing: Hauling heavy loads or towing a trailer drastically reduces gas mileage.
Considering these variables, a reasonable *estimate* for a 1986 Chevy Silverado might range from 10-18 MPG. However, it's crucial to understand that this is a very broad range. A smaller engine, well-maintained truck driven conservatively with no load might approach the higher end, while a larger engine, poorly maintained truck driven aggressively while towing could easily fall below the lower end.
To get a more accurate estimate for a specific 1986 Silverado, you'd need to know its engine size and transmission type, and ideally its maintenance history and typical driving conditions.
