Yeah, MPG is not a simple issue when it comes to cars, a lot of the design of the car goes into, as others have stated.
For instance, I have a 2006 GTO which is a 6.0L V8, and I now get 24mpg out of it. And I even modified it to the point that it puts out 525 rwhp using 60lb injectors. While many v6 and quite a few 4 cyclinders don't get the gas mileage I do. Go figure.
Don't believe the conspiracy theories on MPG, it's all about supply and demand, and what's making money. Gas prices have gone up faster then vehicle makers can develop new cars to handle the shift in consumer demand. Before these gas prices, Americans wanted SUV's, because we didn't care about gas mileage. For the car maker, the money wasn't in gas mileage, it was in big luxuary. Now times are changing, and it will take 3-5 years for most manufacturers to change their lines. In the meantime they are suffering dramatic profit losses. If the car manufacturers and oil companies were in bed together before, they surely aren't now, because the Oil companies are slitting car manufactuers throat.
Lots of good mpg fuel solutions out there, just look around, and don't depend on big business to be the only people with solutions.