Rear tire pressure?

I am currently running 40 psi in my rear tires per the manual. I recently saw that the chassis came from the factory with 55 psi in the rear. I am concerned that the 40 psi is hurting my gas mileage. I have been running between 7 and 9.5 MPG in my Argosy 20 after the carb rebuild. Before that, it was around 8 MPG.



What psi are you guys putting in the rear tires?



(I am running with the factory 70 psi in the front tires.)