* Engine size: E350s came with a range of engine options (V8s primarily), larger engines significantly reduce fuel economy.
* Transmission: Automatic transmissions generally get slightly lower mileage than manuals (though manuals were less common in these vans).
* Vehicle condition: Proper maintenance (tire pressure, tune-ups, etc.) impacts fuel efficiency.
* Driving habits: Aggressive driving drastically reduces gas mileage.
* Load: Carrying a heavy load significantly impacts fuel economy.
* Terrain: Driving uphill or in stop-and-go traffic reduces MPG.
Given these variables, you're unlikely to find a precise number. However, a reasonable *estimate* for a 1999 Ford E350 van in decent condition, with a typical engine and driven reasonably, would be in the range of 8-14 MPG. This is a broad range, and you might see numbers outside this range depending on the factors listed above.
To get a better idea, you should look for specific fuel economy figures based on the exact engine and transmission type found in the particular van. You can sometimes find this information on the vehicle's sticker (if still present), owner's manual, or online resources dedicated to vehicle specifications.
