Compared to my fit, my mom's has very low gas mileage and very poor acceleration. Her highway mpg is about 27 whereas mine is about 36.

Her check engine light is not on and there are no real issues that I have noticed other than the poor performance. Any suggestions as to what might be the problem?

One possible reason for slower performance is that she has aftermarket HFP 16 inch rims with 195's for tires. But I wouldn't think a wider tire/heavier rim would cause that much of a drop.

just let me know if you have any thoughts.
Thanks

 

Did you try swapping cars for a few weeks to make sure it isn't just a difference in drivers?