I have kept meticulous records of my driving habits and mileage over the first 40,000 miles with my Prius. Result: 54.4 mpg. Then I took my the car into the dealer for its 40,000 mile maintenance: new tires, cleaned the intake manifold, alignment, adjust brakes, change oil, replace filters. Now my car is getting about 46 mpg. A drop of over 15%.

I had Toyota recheck everything they did. They say there is no problem. I am pretty sure the tires are the same type that came with the car: Goodyear Integrity. I am using the same tire pressure: 42 psi front, 40 psi rear. I specifically asked about the brake clearance. They said it was fine. They "recalibrated the fuel trim". Still no change. The alignment feels good. My driving patterns have not changed.

I am really at a loss as to what to check.

I know that many people only get 46 mpg with their Prius and I'm sure that is why Toyota is not really concerned. It is frustrating because I know what the car can do and has done for the last 40,000 miles.

Of course, this may have nothing to do with the maintenance work: it could be a coincidence.

Any suggestions?