I have a 2015 Fit, and my son has a 2020. I drive mine to get maximum MPG, and he just drives his - like idling at drive-up windows. His car averages about 5 mpg better than mine.

I loaded my car up with sound-deadening material, yet his car is quieter. His car has that lane warning and crash avoidance technology. Handa has been making improvements. It's too bad I won't be able to buy another new one.

 

It is very much possible that your sound-deadening material adds the weight causing the worse mpg. The fuelly information in you post shows only 0.3 mpg difference.

Each to his own, I'd like to get back to 25 years ago to buy a new car without nowadays technology disputing driver's command of the car and interfering driving.

 

I thought about weight at the time. I weighed one box and multiplied, and the total was insignificant.

Those gas mileage windows under my post are outdated. I don't know how to put the a link for his 2020 on this page.