Corporate average fuel economy in the US for light-duty vehicle sales fell 0.3 miles per gallon in September, according to the University of Michigan Transportation Research Institute’s monthly report. It has to do with the reduced price of gasoline, making fuel-efficient vehicles less important to new car shoppers, according to one of the university’s researchers. For the past year, fuel economy has gone up 1.2 mog to an average of 24.7 mpg.