Tank full

Dollars are meaningless. How many gallons did you use and how far did you drive?

Your car probably averages around 15-18 mpg. Figure out your fuel economy and compare it to those numbers.

2 months ago I bought a 2004 Trailblazer LS. It looked really sharp, fully loaded, and 154,000 miles. Today, a 14 yr old vehicle with 154,000 isn't that bad.First thing i did when drove home was change oil, oil filter, and air filter. Filled her up and just went about my normal driving. After about 2 days I started to see the fuel needle start to nosedive towards E. Fuel range was dropping quickly too. Changed spark plugs, that didn't fix. A mechanic guy i know suggested putting in RAM Air under the hood. Saw greater throttle response but no better on mpg, avg around 8.5. Finally looked at sensor that inserts into ram air intake tube about a foot from throttle body. Asked a guy what it was and he said mass air flow. Bought cleaner, followed instructions and SNAP. Filled tank and watched avg fuel economy rise quickly from reset to 11, 12, 13, 14. Have driven about 20 miles since and it's currently sitting at 12.5. Helluva lot better than 8.5. While the other things I did listed above are good to do, definitely check and or clean maf sensor. It's made a big difference for me.

Not a bad idea to clean throttle body and install a new map sensor. (Manifold absolute pressure)