Better Mileage Car
You can improve the mileage and/or get a better MPG car.
Some 2007 cars had better MPG ratings than the 2008  go figure...

For 2008 Tops is the Toyota Prius 48 MPG city - 45 MPG highway

Here is the order for 2008 cars:

1. Toyota Prius.......................................................48 MPG City - 45 Hwy
2. Honda Civic Hybrid.............................................40 MPG City - 45 Hwy
3. Nissan Altima Hybrid..........................................35 MPG City - 33 Hwy
4. Toyota Camry Hybrid........................................ 33 MPG City - 34 Hwy
5.  Ford Escape Hybrid (Mercury Mariner)............. .34 MPG City - 30 Hwy 
6. Toyota Yaris.......................................................29 MPG City - 36 Hwy
7. Toyota Corolla....................................................28 MPG City - 37 Hwy
8. Honda Fit...........................................................28 MPG City - 34 Hwy
9. Nissan Versa - Scion XD.....................................27 MPG City - 33 Hwy
10. Hyundai Accent..................................................27 MPG City - 32 Hwy

Here a few mechanical tips to increase mileage performance:

1. 10% for a new air filter.
2. 20% increase tune engine
3. 30% lower speed
4. Repair faulty emissions/oxygen sensor

Here is a great site to find cheaper gas in your area http://www.gasbuddy.com/

Calculate or figure out your MPG's this way:

Fill up your gas tank and make a note of the odometer reading.
At the next fill up check the amount of gallons purchased and amount of miles
driven since the last fill up. Divide the miles by the gallons.
This is your MPG. It will change with differing driving circumstaces.

HOT TIP!!!
I started with a 15 - 16 MPG  1998 Astro Van and decided to apply a few tips.
The air filter got replaced and I added tire pressure.
Reducing the excessive weight helped. (250 Lbs will save 1 MPG)
There was a lot of coasting downhill and I refused to touch the brake unless I had to
while driving as if I had an egg under my right foot.
I drove the highway at a speed where the van was in top gear
but the engine revs were lowest.

This radical change in driving habits of too much speed and too much braking got me
22.1 MPG from New Bedford, Ma. to Poughkeepsie NY.
There was a lot of gas in the tank when I got to Poughkeepsie and I continued
the next day back to Massachusetts and got to Raynham before filling up.
There wasn't much gas left but this guy had gone 453 miles on that tank with
whatever little was left in it...... Good Luck.

Here are some valuable tips for saving money on gas etc.

ScanGauge scan gauge 

How To determine your MPG

230 MPG car

Best MPG car

Better mileage car

Save Money On Gas <---Highly recommended page