Low miles per gallon

Hello,
That is low, First check the air pressure in the tires next I would replace the MAF sensor which becomes contaminated causing false reading effecting the performance and the mileage. Here is a guide that should help.

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

Here is how it is done for your car (below). Please run this test and get back to us.

Cheers, Ken