* Engine: The 2000 Dodge Ram 3500 van came with different engine options (likely a V8 or possibly a V10). Larger engines generally get worse gas mileage.
* Transmission: Automatic or manual transmission will affect fuel economy.
* Driving conditions: City driving will yield significantly lower MPG than highway driving. Terrain, speed, and even weather can impact mileage.
* Maintenance: Properly maintained vehicles generally get better gas mileage.
* Load: A fully loaded 15-passenger van will get considerably worse gas mileage than an empty one.
You're unlikely to find a precise MPG figure without knowing the specific engine and transmission. However, expect very poor fuel economy. Think in the range of 8-12 MPG combined (city and highway), and possibly lower depending on the factors listed above. This is a very large, heavy vehicle.
