Hi I bought a 2000 Monte SS (L36 3.8L) about 4 months ago, ever since I've had it I've been getting 14-16 mpg. I do mostly city driving, but this seems abnormally low. It's sitting at ~114,000 miles. I don't think any maintenance has been done as I replaced the air filter and the old one was way over due. I have had to replace the Intake manifold.....a common problem apparently. I am changing fuel filter, spark plugs, and 02 sensor as well as cleaning the MAF and Throttle body, anything else I should do. I do have the service vehicle soon message flashing on the screen.

 

You can replace the PCV and check the fuelpressure regulator too.

 

I believe this can give you a good list to review and help you out:
https://montecarloforum.com/forum/fw...0-miles-46078/

 

im also getting bad mpg, i just did a full tank with since ive changed the fuel pump and ive gotten like 215 miles....im gonna do seafoam and hope that helps

 

Something to point out, I believe during winter, gas stations tend to switch to a "winter" blend fuel (I believe it contains more ethanol). If that is truly the case, it has a negative impact on your MPG.