* V6 engines generally offered better fuel economy than the V8s. You might see EPA estimates in the low-to-mid 20s mpg combined (city and highway).
* V8 engines would have significantly lower fuel economy, likely in the teens (mpg) combined, possibly even lower depending on driving style and engine size.
To get a more precise estimate, you'd need to know the *specific engine size* (e.g., 2.8L V6, 5.0L V8, 5.7L V8, etc.) of the particular 1989 Firebird in question. Even then, actual mileage can vary based on driving habits, vehicle condition, and other factors.
