added a couple electric bikes
OH NO,,,.... I had my two electric assist Trek bikes on the back of my Gen 1 volt, me, wife, and camping gear, half a tank of gas and when weighed we were within 35 pounds of the GVWR... something to think about. My MPG also went from the low 40's to the low 30's... ...
Also weight deforming the tires differently (both "down" and "outward"), increased power to maintain "spritely" acceleration, etc. Many factors all play in this, but all come from a few hundred extra pounds in the car.Also 10 mpg drop due to the dirty aero of bike hanging off the back seems like a lot.
Did you measure a round trip, accounting for wind and elevation change?
A one time, one way trip is not ideal for measuring MPG.