I have my own personal strategies for generating the very best gas mileage available for your car. I have listed the five most important areas for optimizing performance and increasing your gas mileage at the same time! I generated this list from 20 + years of experience and specializing in Engine performance with certifications from ASE in this field.
1. Replace all of your spark plugs after 2 years or 30,000 miles.- I recommend changing your spark plugs with the manufacturers recommendations. Almost all manufacturers use the Platinum spark plug because they are built to last for a long time. The older spark plugs only lasted 12 months or 12,000 miles without being inspected or replaced. The electrodes would burn down increasing the gap for the spark to jump.
2. Replace your gas filter every 12,000 miles.- Most fuel filters are in line. This means if you follow the fuel line from the gas tank all the way up to the intake manifold, you will find the fuel filter located in this area. Most cars carry a 35 to 45 PSI pounds of fuel pressure through this filter. Any restriction by a few pounds will drop your power and performance output considerately. (means having to press the gas pedal more)
3. Replace your oxygen sensors every 60,000 miles.- The o2 sensors monitor and read the amount of oxygen content coming from your engine. Then in return they tell the computer how to adjust your injectors to compensate for the readings. Slow or sluggish 02 sensors will not respond to the changes as quickly as they need to be compared to new ones.
4. Clean Your Fuel Injection System every 12.000 miles.- A lot of automotive shops offer this type of service to the customer. What this usually includes is, cleaning your injectors with a very strong additive, cleaning up and around your throttle plate area, and cleaning your intake manifold with compressed air and a very strong cleaning agent. You would be surprised to see how much carbon, tar, and varnish is clinging to your fuel system walls and throttle plate. This carbon build up will actually absorb the air and fuel mixtures from entering your engine.
5. If Equipped, Change Your Timing Belt Every 60 to 90,000 miles.- Your timing belt is usually overlooked because you can not visually see the condition it is in. A worn and stretched timing belt will also rob your engine of the power it needs. After 60.000 miles the belt begins to crack and starts to actually stretch like a worn rubber band. The timing of your camshaft to your crankshaft will not be as good as when the belt was new.