I got an '07 Prius a couple weeks ago and of all the info I've come across on the 'net (along with ideas of my own), I reduced the as-delivered weight of the car by 40 lbs. by taking out the rear plastic bin that is above the spare, the carpeted deck that lives on top of that, a small plastic box lid to the left of this deck, a couple of tools that aren't needed, the owners manual, the rear cargo net, all of the head rests except for the driver's (I never carry a passenger), the floormats (again, except for the driver side) and a couple of silly carpet and shelf inserts in the dash and glove box. I'll report any increase (or decrease!) in mileage I see.
I'm seeing, so far, 60 mpg on the highway and about 50 in the city, although I'm sure the numers are getting better due to some breaking in. And these are my own numbers, using the same pump at the same station, 87 octane Chevron.
I also increased the tire pressure to 45 psi.
I also think at the first oil change I'll switch to Mobil 1 0W-30.
Any folks out there use/know about using this weight oil in the Prius? It is supposed to be better for hybrids, due to the frequent stops and starts of the engine. A thinner oil would spread around the bearings faster.
Although, Toyota says to use 5W-30.
Finally, anyone know anything about increasing the battery capacity by adding rechargable AA's via the 12 volt power jack in the dash? Seems, at least on the surface, that one could construct a simple box, fill it with a hundred or so Ni-Mh AA's, charge this assemblage at home overnight and "sip" from it while driving the next day. I can imagine the car's software would be a problem, as it would not know of this increase in capacity.