Here are some very good tips on improving your vehicle's Fuel Economy / Increase Fuel Efficiency / Mileage. With increasing fuel prices it is becoming more and more prudent to use them.
Use your gears wisely.
Driving in the highest gear possible without labouring the engine is a fuel-efficient way of driving. A vehicle travelling at 60kmph in third gear uses 25 percent more fuel than at the same speed in fifth gear
Think ahead! By applying light throttle and avoiding heavy braking, you can reduce both fuel consumption and wear and tear. Try to predict traffic at junctions and when in queuing to avoid accelerating and then braking. Research suggests driving techniques can influence car fuel efficiency by as much as 30 percent.
Switch off your engine
There are two schools of thought on this one. Switching your engine off for short periods of time can actually increase fuel consumption, as it requires more fuel to get the engine started. Also your catalytic converter will no longer be running at full temperature and so your car will be less efficient, increasing the amount of pollution you cause. However if you are stopped for more than a few minutes then your car will simply burn less fuel with the engine stopped.
Drive off promptly to prevent wasting fuel
Don't leave your engine running when you first start up. Drive off straight away if you can, but drive gently until the engine has reached its normal operating temperature. This doesn't increase fuel efficiency as such, but it does mean your engine is switched on for less time.
Lighten your load
Think carefully about what you need on a journey. if you do not need something, do not pack it. Remove roof racks if not needed. The lighter the load, the lower the fuel consumption, and emissions, and the higher the fuel efficiency.
Tyres effect fuel efficiency
It is estimated that about 50% of tyres on the road are under inflated. Aside from increasing the rate of wear, this wastes fuel and decreased your fuel efficiency. Check your tyre pressures every fortnight. Worn tyres will also decrease fuel efficiency (and your safety!), so check the tread regularly. If you are replacing tyres then consider some of the newer 'Eco' tyres that are designed specifically to increase fuel efficiency.
Driving with your windows open drastically reduces your fuel efficiency, far more so than putting the air conditioning on when motorway driving. So in those hot summers(?) preferably keep the windows shut, and the air conditioning on if you want to keep cool. Of course the air conditioning decreases fuel efficiency too, so try not to over use it.
Invest in a new fuel efficient car
New cars come in all shapes and sizes, but it is possible to pick a new car that can greatly reduce your fuel bill, and your fuel emissions.
Size matters. Choose an economical car - small cars use far more fuel efficient and produce lower emissions than large cars.
Drive the most fuel-efficient car that meets your needs. Compare models and classes. Even similarly sized cars can vary in fuel efficiency by up to 45%.
Consider diesel engines (with a particulate trap), and LPG (Liquefied Petroleum Gas) and CNG (Compressed Natural Gas) fuelled cars - all have lower CO2 emissions than standard petrol cars.
Consider 'hybrid' vehicles - they combine a conventional engine with an electric motor and battery. These offer reduced fuel consumption and CO2 with potentially lower emissions of all pollutants.
If your going to buy a diesel, ensure it is a new 'common rail' type, as these are approximately 10% more efficient than older diesels. also replace (or clean if applicable) air cleaner elements as often as is required by your vehicles servicing schedule.
Regluar Maintenance maintains fuel efficiency
One of the most common reasons for a drop in fuel efficiency is a dirty intake filter. This will decrease the amount of air entering the cylinders of the engine resulting in incomplete combustion. Check the filter regularly to ensure that it is clean.
Ensure your spark plugs are in good condition. Renew the plugs and wires at intervals specified by the owners manual. This will keep all cylinders firing properly resulting in higher efficiency.
Change the lube oil at intervals specified by the owners manual. Use the recommended oil only especially in newer cars. Use of an engine flush before changing the oil will help to get rid of a lot of the dirt that collects in the engine that a normal oil change will not remove. On older engines it is advisable to use an oil treatment agent. This basically thickens the oil which creates a better seal between the piston and the liner, preventing blow past and consequent loss of combustion pressure, resulting in higher fuel efficiency.
Exhausts alter fuel efficiency
Most cars have special sizes for the exhaust. When cars are reasonably old the silences has to be changed. The garage people always try to fit a size that they have in the garage it self. Which might not be the exact size recommended for the car. The wrong size a bigger or smaller silencer size effects on the MPG of the car and the HP of the car. It may be cheaper to put another size than your recommended size for your car but on the long run it will cost you in many ways, especially on fuel consumption. Always put the recommended size of the exhaust that is indicated in your car manual because the car company knows how to optimize the performance of your car.