low mpg for 2002 Prius

I read the "2004 Prius = BAD MPG??!!" discussion (http://www.automotiveforums.com/vbulletin/t157017.html). It started with the low mpg of a 04 Prius but followed up with the heated discussion between the VW Jetta TDI and the Prius. What missed are the discussions on

1. Why is there such a high discrepancy between the Toyota rated mpg and the actual mpg to some Prius?
2. Is there any way to fix the low mpg problem?

Let me relate these questions to my experience.

I have driven two Prius now. One is a 2000, which was totaled by a SUV from the rear after 7 months, and the other one is a 2002. The 2002 one was constantly having 48 mpg with mix city and freeway driving. However, the 2002 one is getting only 40 mpg with more city than freeway driving. The only difference between the two is that the 2002 one has daytime running light and side airbags. Why is that the 2004 has worst mpg with a more favorable driving condition?

Based on my reasoning, I can think of two possible explanations:

1. Because of the daytime running light, the gas engine has to be on more often to produce juice for the battery (or diverts less juice to the rechargeable battery). With the 2002 Prius, before the car stopped in front of a red light, the engine already shut itself off. However, the 2002 Prius often is still on after I stopped. Even of it shuts off, it will quickly starts up again. The computer must think that the rechargeable battery is running low.

2. Another observation is if the interior fan is set to run at any speed, the engine will almost always on. As soon as I turn off the fan, the engine stops.

Since I no longer have my 2000 Prius, I can only related to it by recollection. I remember when I was driving in the congested stop and move traffic, the car will mostly use the battery for driving until the rechargeable battery got to be about 1/2 to 1/3 juice left (as shown on the display screen). I could hardly replicate this condition with my 2002.

My questions are:

1. What is the problem with my 2002 Prius? I have the Toyota checked it twice but was told that there is nothing wrong.

2. Can I re-route the interior fan by connecting it to the 12V battery so that it does not trigger the gas engine to be on unnecessarily? If it is possible to do, how to do it?

the interior fan probably runs off the engine belt so that's probably why the engine turns on. also, your mpg may vary according to what temperature the weather outside is. if its cold, you will get a lower mpg than if it is warm outside because the air going into the engine doesn't get heated quickly enough to combust cleaner/more. blah blah i dont know what im saying :) also, check your tire pressure because gas can be lost there. and if you use synthetic oil, you can push out 1 or 2 more mpg

What some people don't understand is that any gasoline vehicle can lose up to 20% of it's gas mileage just from aggressive driving. More info here - http://www.fueleconomy.gov/feg/FEG2006_GasolineVehicles.pdf. It's the government's latest report.

I have also heard that the EPA's judging of mileage (which is done for all cars) is out of date and overrated.

Here's another good article from MSN.com.

http://autos.msn.com/advice/article.aspx?contentid=4023628&src=LP%20utes