Hello all I have been reading over quite a few of the posts in this section to try and get some ideas as to why my Prius's MPG has dropped. Right now I am seeing roughly 41 MPG and that is after changing the spark plugs with brand new NGK Iridium's, Air intake filter and did an oil change since it was due for one. I have driven the car roughly 2,500 miles since all of this stuff was done and it just seemed to continue to drop to the 41 MPG mark. What I have noticed though is that when the motor turns off it shudders and the when it restarts while the car is in park the car will roll back and forth slightly. I have also noticed that the car seems to struggle to get up to the posted speed while climbing an incline and also while the car idles in park or at a complete stop there seems to be a bit of a miss fire. Could that be caused by a bad coil? Because I have tried everything short of taking it to the dealer which I really do not want to do again and be told there is nothing wrong with it when I know there is. Any help with this issue would be greatly appreciated. Thank you in advance!