One way to deal with higher gas prices is to drive less. Here are a couple of more practical recommendations that can improve your gas mileage significantly. Few vehicles will have ALL of these problems, so it would be unfair to compound these benefits, but some may apply to your vehicle right now!
Keep Your Engine Properly Tuned
Fixing a serious maintenance problem, such as a faulty oxygen sensor, can improve your mileage by as much as 40 percent. Fixing a car that is noticeably out of tune or has failed an emissions test can impove its gas mileage by an average of 4 percent (though results vary based on the kind of repair).
Check & Replace Air Filters Regularly
Replacing a clogged air filter, which keeps impurities out of the engine, can improve your car's gas mileage by as much as 10 percent.
Keep Tires Properly Inflated
Keeping your tires inflated to the recommended pressure can improve your gas mileage by around 3.3 percent. Under-inflated tires can lower gas mileage by 0.4 percent for every 1 PSI drop in pressure of all four tires, because they increase the amount of rubber that is touching the road at one time, increasing rolling resistance and wear on tires. If tires are 8 pounds under-inflated, for example, rolling resistance of the tires increases by 3%.
Check Wheel Alignment
If wheels are just 1/4" out of alignment, an add 2% to fuel consumption. Have your alignment checked every time you rotate your tires.
Use the Recommended Grade of Motor Oil
You can improve your gas mileage by 1-2 percent by using the manufacturer's recommended grade of motor oil. Oil that is too thick or too light can provide the wrong level of friction reduction for your particular engine. For example, using 10W-30 motor oil in an engine designed to use 5W-30 can lower your gas mileage by 1-2 percent. Using 5W-30 in an engine designed for 5W-20 can lower your gas mileage by 1-1.5 percent. Look for motor oil marked "Energy Conserving" on the API performance symbol, which shows it contains friction-reducing additives.
Check your Thermostat
A cooling system thermostat stuck in the open position, causing the engine to run too cool, can reduce engine efficiency by as much as 7%.
Go Easy on Gas Pedal
Smoother acceleration lets the engine work most efficiently. And stay of the accelerator. For every 10 km per hour you go beyond 90km/hour, you'll lose about 1.5 km per litre in fuel efficiency.