There’s one more test before going ballistic.
Road trip with NO stops between fillups, no topping off, just allow the gas pump handle to click off, then that’s it.
After about three or more fillups w/o stopping or slowing for traffic, then compare against the 34 mpg advertisement to see if your car is dragging butt, while the average ones are not.
Remember long ago when these “testers” that compile those average mpg figures … stated their disclaimer? Not all cars will be in this “average” range. You & I know that driving condition vary widely across this country as well = affects mpg.
Please post your road trip results!