* The specific vehicle: A large truck or SUV with a 7.4L engine will get significantly worse gas mileage than a smaller vehicle with the same engine.
* Driving style: Aggressive acceleration and high speeds drastically reduce fuel economy.
* Road conditions: Driving uphill, in stop-and-go traffic, or on rough roads all decrease mpg.
* Vehicle maintenance: Proper maintenance (tire inflation, tune-ups, etc.) impacts fuel efficiency.
* Year and model: Even within the same engine size, improvements in engine technology over the years can lead to better fuel economy.
A 7.4L engine is typically found in large, powerful vehicles, and therefore you should expect relatively low mpg figures, likely in the range of 8-15 mpg in real-world driving conditions. However, it could be lower or slightly higher depending on the factors listed above. You'd need to specify the make, model, and year of the vehicle to get a more precise estimate, and even then, it's just an estimate. The EPA estimates for the specific vehicle would be the best source of information.
