I am a newbie to this site, but love my prius. I have noticed a significant (15 to 20%) drop-off in mpg in the last 6 months or so. My 2006 prius at 95,000 miles is just short of the warranty on the battery pack. I brought it in to the dealership and they ran the routine computer diagnostics and said everything looks good. I fully expected them to tell me that the performance on the batterpack had fallen off, so I was a bit put out. The guy actually got a bit defensive with me when I asked him some further questions about what the criteria are for determining whether the battery back was performing as it is supposed to in order to get the maximum MPGs. Is it possible that the diagnostic machine would indicate that everything is fine, but the battery pack NOT be fully up to par? Sadly, I'm not sure I trust my dealer with acknowledging a functioning, but poor performing battery pack just short of the warranty period being up. Any comments or suggestions are greatly appreciated.