I have found there are a few modifications that can make a great deal of difference in your quest for better fuel efficiency/gas mileage. Combining some or all of these can increase your MPG significantly. You will just have to decide if the cost outweigh the benefits.
1. Switching to synthetic oil. Can improve gas mileage up to .05 - 1 MPG
2. Switching to synthetic transmission oil. can improve gas mileage by 1% - 2%
3. Cold Air Intake - Can improve HP and improve gas mileage from .05 - 3 MPG
4. Cat Back Exhaust can improve HP and improve gas mileage from .05 - 3 MPG
5. Performance Chip/Tune can significantly improve HP and improve gas mileage from .05 - 4 MPG (May also decrease gas mileage depending on how heavy your foot becomes)
6. Underdrive Pulleys - Can increase HP and improve gas milage from .05 - 2 MPG
7. SeaFoam - Can increase HP and improve mileage by removing build up and junk from your top end.
8. Injector Cleaner - Can improve mileage by remove build up/junk from injectors.
9. Tire Pressure - Increasing tire pressure can help improve mpg, lowering your "rolling resistance" by over inflating your tires can help reduce drag and increase fuel efficiency, every 1lbs of pressure helps by .4% so going from 32 lbs to 37 increases fuel economy by 2%. Never exceed the manufacture max pressure (most are 44lbs)
*Please note: all numerical values will vary and will depend on your make/model/and any modifications already on your vehicle.
Car Maintenance
Fuel and Fire
1. check/replace Spark plugs
2. check/replace spark plug wires
3. check/replace cap/distributor/ coil packs
4. check/replace air filter
5. check/replace fuel filter
6. Ensure all check engine lights/codes are properly addressed
7. Ensure there are no emission vacuum hose leaks
Other things you can do.
1. Use Cruise Control often - Cruise control was designed to optimize your milage and power/speed ratio. it will use the most appropriate amount of fuel to maintain the velocity of the vehicle. Use it often!
2. Cut off Air Conditioner when driving - (Use with caution especially if you have a significant other that is always hot) but this can save significant mpg on a long trip or commute.
3. Weight Reduction - Removing rear seats and spare tire can lighten your vehicle from 50-100 lbs allowing your motor work less to get up to speed, increasing fuel efficiency.
4. Drive slower/Lower RPM - Your RPM gauge looks different driving at 75mph vs 55 mph...The Lower your rpms are the less fuel you will use.
5. Gearing -"Installing a set of lower numerical gears will translate to higher fuel economy. Switching from a set of 3.23s to 2.73s will lower your auto’s normal operating rpm range during driving using less fuel. NOTE: You car's acceleration performance can feel greatly decreased because of lower gears
6. Waxing (umm for your car..) - Reducing wind drag will help increase MPG, it may not be noticeable on a per tank basis but over time and in conjunction with other modifications you can realize better result.