Our previous article talks about adopting good driving habits in order to squeeze the maximum work out of the petrol or gasoline we use for our vehicles.

In this article, we will explore more ways of achieving that - by good maintenance of your vehicle.

Good maintenance not only ensures that the vehicle does not breakdown when you least expect it, but it also has a strong influence on the fuel economy.

The condition of the engine plays a major part in fuel saving. We do not want piston rings that leak, perhaps due to wear down of the rings or the cylinder bore. This will waste some of the power that should instead be used to drive the crankshaft of the engine. Similarly with inlet and exhaust valves. These should not leak because the power developed in the engine cylinders can be lost through them. A good overhaul will greatly improve the condition of the engine.

When you are satisfied that the engine is in good condition, we should then look at the tuning of the engine. It is very important to do it right. It directly influences the combustion efficiency.

Correct engine timing means the fuel can burn completely and the exhaust gas led away completely. It means that the combustion cycle of an engine follows the optimum design, i.e. fresh air is mixed at the correct ratio with the fuel to provide a good explosive mixture, the ignition source or spark plug is activated just at the right moment, and the inlet valves and outlet valves are opened at just the correct angle of the cycle.

If there is some delay in the timing, this will affect the combustion. Some of the fuel will remain unburnt, and are then led out through the exhaust pipe. This is sheer wastage.

Improper combustion in the engine can be detected by an emission test. A high percentage of carbon monoxide in the exhaust is a sure sign of incomplete combustion.

Fixing a car that is noticeably out of tune can improve its gas mileage by an average of 4 percent, though results can vary based on the kind of repair and how well it has been done.

Combustion of any fuel needs oxygen. Replacing a clogged air filter can improve your car's gas mileage by as much as 10 percent. The excess air for combustion helps ensure that all the fuel has been burnt.

Although it can reduce the air for combustion if it becomes choked, the car's air filter is necessary. It keeps impurities from damaging the inside of your engine. It therefore helps to prevent abrasive particles from wearing down the moving parts of the engine, particularly the piston rings and the cylinder bore. Naturally, this will help keep the engine in good working condition and lengthens the frequency of an engine overhaul.

The next influence on the fuel economy is the tire pressure. Under-inflated tires can lower gas mileage by 0.4 percent for every 1 psi drop in pressure of all four tires. Proper inflated tires are safer and can last longer. Your gas mileage can be improved by around 3.3 percent by keeping your tires inflated to the proper pressure. However, you must not over-inflate the tires. Over-inflated tires can cause bumpy rides and can even burst. This is dangerous.

With so many moving parts in the engine and transmission shafts, the lubricant does have an impact on the fuel economy. You can improve the gas mileage by 1~2 percent by using the manufacturer's recommended grade of motor oil. For example, using 10W-30 in an engine designed to use 5W-30 can lower your gas mileage by 1~1.5 percent. When choosing engine oil, look for oil that contains friction-reducing additives. These are usually labeled as "Energy Conserving" on the API performance symbol.

These are some aspects of engine maintenance that can help you reduce your gas consumption in your vehicle.