Yeah, our bikes were both on the back of the Prius for the drive. Bad move. Two bikes on the back of a Prius acts like a sail. Our MPG dropped to BELOW what the Matrix was getting (we drove both cars - too much stuff with two 70+ lb dogs). We found an ACE hardware and bought a socket set to switch the bikes to the Matrix and were amazed at the change in gas milage. It barely lowered the Matrix MPG at all and the Prius went right back up to where it belonged. It was all about aerodynamics and the shape of the two cars (and the engine size)... Live and learn.

Oh, and I have NEVER seen dirtier bikes before! We spent hours cleaning them up once we got to our destination. I am SOOO thankful we opted to take the 'rain' bikes on the car and not our nice road bikes!