I can single-handedly increase the gap! I just finished a round-trip drive San Diego <-> Phoenix at speeds usually between 82 and 88 miles per hour, and I have to say, this car gets ludicrously bad mileage (for a car of this type) when going anything above 80; I haven't calculated the final trip mileage but it's likely around 33 mpg. The car's weak engine just could not keep up, especially when scaling some steep mountains where I had to floor it at 6000 rpm just to maintain 70 miles per hour. Also, the steering is very wobbly and nervewracking above 80.

Although my recent oil change might be partly responsible; since I plan to trade the car in soon, I just used official Honda 0W20 oil, which is mineral crap.