* 4.5L V8: This engine generally had a fuel economy rating in the low to mid-teens MPG (miles per gallon) in combined city and highway driving. Expect somewhere between 14-17 MPG depending on driving style and condition.
* 4.9L V8: This larger engine would likely have slightly lower fuel economy than the 4.5L. Expect something in the range of 13-16 MPG, again varying by driving habits and vehicle condition.
Important Considerations:
* Driving style: Aggressive acceleration and high speeds drastically reduce fuel economy.
* Vehicle condition: Properly maintained vehicles (tune-ups, properly inflated tires, etc.) tend to get better gas mileage.
* Terrain: Hilly or mountainous terrain will reduce fuel economy.
* City vs. Highway: City driving generally yields lower MPG than highway driving.
To get a more precise estimate, you should check the owner's manual for the specific fuel economy ratings for the engine in *your* 1990 Cadillac Brougham. These figures are usually provided in both city and highway driving scenarios.
