* Engine size: The 1999 Tahoe came with several engine options (a 5.7L V8 was common, but others existed). Larger engines generally mean lower MPG.
* Transmission: Automatic or manual transmission will affect fuel economy.
* Driving habits: Aggressive driving, frequent acceleration, and idling all reduce MPG.
* Tire pressure: Properly inflated tires improve fuel efficiency.
* Vehicle condition: Proper maintenance contributes to better gas mileage.
* Terrain: 4x4 use, especially off-road, significantly reduces fuel economy.
Therefore, there's no single answer. However, you can expect somewhere in the range of 10-15 miles per gallon (mpg) combined city and highway driving for a 1999 Chevy Tahoe 4x4 with a typical V8 engine. Highway driving might yield slightly better results, while city driving will likely be considerably lower.
To find a more precise estimate, you could consult the original owner's manual (if available) or look up fuel economy data for that specific year, model, and engine on websites like the EPA's FuelEconomy.gov (though data for older vehicles may be limited).
