Caymen is correct. No amount of modifications will beat just not having to make a payment. That does not sound like gas savings, but it does save you money.
If you were to go the route of modifying your ST with exhaust, intake, reprogrammers, etc you will spend a lot of money for a very small return if any at all. Take the money you would spend on mods and use it to buy gas, or better yet buy stock in one of the big oil companies
There are no simple or easy fixes for the oil/gas prices. The only thing driving the market is demand and speculators. When the demand goes down, the price goes down.
I know a lot of people will argue that improvements that gain HP will also improve mileage...and for the most part that is true as long as you keep a light foot and don't use the new HP. In reality, a vehicle tunded for HP rarely returns very little in gas mileage improvements. The biggest factor in poor gas mileage is driving habits, driving habits, and driving habits... followed by traffic and weather conditions.
A better investment would be some kind of a trip computer that gives you gas mileage readouts so that you can actually see what kind of driving gives you good gas mileage and what kind really kills your mileage.
My new car has a trip computer that gives average MPG. If I accellerate hard I can actually see the MPG drop by about 0.1 MPG about every 25-30 feet I go down the road. If I accelerate very gradually the is still a drop in MPG but it's 0.1 MPG every 150-200 feet and streatches out even longer as momentum builds.
While I always thought that I had good driving habits, that onboard computer has allowed me to get a consistant 28-29 MPG on the highway on a vehicle that is EPA rated to only get 25 on the highway.
So if I were going to invest in money to save gas, I would buy some kind of trip computer that calculates average and instantanious gas mileage readings...you will be amazed at how much your driving habits can change your mileage with just little changes.
...Rich
