Aerodynamic drag is a real drag
 

As in, it drags down mpg's.:what:
We drove our '14 RDX base fwd on a 400-mile each way trip. Almost all on interstate 5 in California. Our daughter started her first term of college and we dragged (okay, enough puns) her belongings to the dorm. It maybe added 120 pounds, but the chief cause for low mpg's came from her cruiser mounted to a rear rack. Big tires, big fenders = catching mucho air.

Tires: upped to 37 psi, which possibly caused a 2% unfavorable odometer variance, measured against the tiny mile posts along the freeway.

Avg speed: both ways came to 71 mph, even factoring in hills and minor clogs of traffic.

Other considerations: only a few times did we encounter any wind gusts. Typically side-angled. Copious use of the cruise control. Avoided any harsh accelleration, opting to mostly drive in the slow lane. Thought about drafting big rigs, but decided not to since it would screw up my "analysis."

Miles per gallon, to campus: 26.2
Miles per gallon, return trip: 29.2

I did something similar with a Toyota Sienna years ago, with several bicycles mounted atop the vehicle. That devasted mileage to the sub-20's!

Incidentally, I never reset Trip B on the odometer from the day I purchased my RDX. It displays 26.1 over 17k miles. Probably 75% freeway miles, but many hills and fast jaunts with my leadfoot. :wish:

Very happy with the RDX. No significant complaints. Would buy another in a heartbeat. No interest in paying 7 to 10k just to be unique.

What's the best way to keep the tire pressures to maximize gas mileage? Should each tire have the same pressure?

I would suggest taking the manufacturer's recommendation: 35 in front 33 in back (I believe). The additional in the front is for the extra weight in the front.

Two things...One and most important, when you have a big box driving through the air, slower is better...try driving the speed limit (I know, what a concept!!LOL) and you will find your gas mileage goes up several MPG. The other is, it may have been affected by the gas, different stations, different areas, sometimes use different mixes, especially if you cross state lines. Last, if you really are concerned, shop for a tire that maximizes MPG...it will be a little louder and not corner as well, but that's what you sacrifice for max fuel economy.