* Engine: The specific engine fitted (e.g., diesel, petrol, and their various power outputs) significantly impacts fuel consumption. Diesel engines generally offer better fuel economy than petrol.
* Load: A heavier load will drastically reduce fuel efficiency.
* Driving style: Aggressive acceleration and high speeds consume more fuel.
* Terrain: Driving uphill or in stop-and-go traffic reduces MPG.
* Vehicle condition: Proper maintenance is crucial for optimal fuel economy.
* Tyre pressure: Under-inflated tires increase rolling resistance, impacting fuel economy.
Therefore, it's impossible to give a single definitive "miles per gallon" figure. However, you can expect a range of 20-35 MPG (UK gallons) or 24-42 MPG (US gallons) for a diesel engine under reasonably favorable conditions. Petrol engines will likely deliver significantly lower figures.
To get a more precise estimate, I recommend checking official fuel economy figures from Ford for the specific year and engine of the Transit T350 LWB you're interested in. Real-world fuel economy will likely be lower than the manufacturer's claimed figures. You can also find real-world MPG data from owner reviews on sites like Parkers, AutoTrader, or similar automotive websites for your region.