This not a gimick. The First and easiest thing that you can do to reduce emissions and increase your fuel mileage is to use gasoline that does not I repeat DOES NOT CONTAIN Ethanol. It reduces fuel millages by up to 2 MPG thus it increases emissions not decreases. Also use the highest octane or cetane(diesel). It is a little more expencive but it is really cheaper because you can go further on $20.
Step 2
Install a cold air intake or short ram intake. Coold air is better but not avaiable for some cars. This increases the air flow on the intake side of the engine and reduces pumping energy. Lets take a step back to discus the Internal Combustion Engine. It is a giant air pump in all reality. With stock intake and exhaust it is like you breathing through two coffee stir sticks. One you breath in with and one you breath out through, this is very difficult and if you don't believe me try it. Once you have replaced your intake you are breathing in normally, but still out through a stir stick. To install such an intake only philip and regular headed screw drivers, a small socket set, and possibly a torcs driver set. It is a simple 2 hour install in most cases. Costing between $70 and $400 depening on model and brand of kit. This is an average 2-4 MPG increase.
Step 3
Exhaust. Install a high flow cat back exhaust. This means replaceing all of the exhaust tubing and muffler behind the catalytic converter (required on most automobiles manufactured after 1972.) This is pretty strate foward except that is requires a lift for most cars and professional installation is required. Now you are just breathing out through your nose so to speak. Besides the lift a socket set is useually all that is required. Costing between $100 and $500 depending on the car and setup you choose. 1-3 MPG increase.
Step 4
Exhaust continued. Install tubular headers and high flowing catalytic converter. Now we are breathing completely normal. However in some states these modifications are illegal, so check you local listings. The catalytic converts runs $150 and the headers can run from $100 to $300 depending on your car and the brand of the components. Both of these install with just a socket set useually but a poor header install can mean exhaust leaks so professional install is recomended again. 1-2 MPG increase.
Setp 5
This last step is to increase drive train efficiency. It you have a manual transmission it is recomended you get a multiple puck clutch and a lighter flywheel. This will make your car more difficult to drive. For an auto transmission get a shift stiffener, these are available from companies such as Jet Tuning. They make your car shift faster and harder extending the life of your transmission by reducing friction. Also for a minor modification you can upgrade to lighter than stock rims to help reduce rolling stock and thus the resistance to acceleration.
There is of course the most common sugestion, get a tune up, use synthetic oil. But don't however, fall for spark plug gimicks. Platinum and Irridium Plugs are for mini vans and other cars that are not properly maintained. Because they last longer than standard copper plugs. Put in a nice set of high performance copper plugs like NGK V-Power and you'll be all set, just don't expect any gains in fuel mileage here. And of course keep you tires properly inflated. DO NOT OVER INFLATE THEM! You can increase your final drive ratio (slower acceleration and means more petal to accelerate) by doing so and its just bad for the tires.
Other modifications that you can do are to reduce weight, remove you stereo, remove your air conditioning. You could also remove your airbags (personally a bad idea). But you can get alot of money for them, just don't get caught uninstalling them because its illegal to unistall them.
If you have completed these mods you now have a car that gets 4-9 MPGs more than stock, has more horse power, and sounds very nice. Not to mention you have a sweet looking pair of rims.
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