Several years ago, when I bought my 2004 Tahoe K1500 LT w/the 5.3L V8 FFV, it averaged 13.5 mpg in town. Since then, fuel economy has been gradually decreasing, and now it averages 10.9 mpg in town. I have performed all the scheduled maintenance, and keep the tires at the proper level of inflation. Why might this be? Thanks
Bad gas mileage is usually tied to an oxygen sensor or a leak near it. The sensor sees a lean condition and adds gas that is not needed. Other possibilities are blockages in the air intake path or exhaust path.