* Engine size: The 1987 Silverado came with a wide range of engine options, from small inline-sixes to large V8s. A smaller engine will naturally get better gas mileage than a larger one.
* Transmission: Automatic or manual transmissions also affect fuel economy.
* Vehicle condition: Proper maintenance, tire pressure, and overall vehicle condition impact MPG.
* Driving habits: Aggressive driving significantly reduces fuel economy.
* Payload and towing: Hauling heavy loads drastically lowers MPG.
Therefore, it's impossible to give a single MPG figure. However, you can expect a range. A smaller engine Silverado might achieve 15-20 MPG on the highway under ideal conditions, while a larger V8 might only get 10-15 MPG, or even less depending on the factors listed above. City driving will always yield lower MPG than highway driving.
To get a better estimate for a *specific* 1987 Chevy Silverado, you'd need to know the engine size and transmission type. You could also consult resources like the EPA's fuel economy database (though data for vehicles that old might be limited or nonexistent).
