You won't find one definitive answer. However, you can expect city mileage to be in the low teens (mpg) and highway mileage in the low to mid-twenties (mpg). It's likely to be closer to the lower end of those ranges if the vehicle is not well-maintained.
To find a more precise estimate, you could:
* Check the original owner's manual: If you have the manual for that specific car, it might list EPA estimated fuel economy figures.
* Search online used car listings: Look at listings for similar 1994 Thunderbirds with V8s. While not perfectly accurate, these often include fuel economy information reported by sellers.
* Use a fuel economy calculator: Several websites and apps allow you to estimate fuel economy based on various inputs. However, you would need to know the exact engine size and other specifics of the car.
Keep in mind that any estimate will be an approximation. Actual mileage will vary.