How to improve fuel economy

I drive a Volkswagen Golf 5 1,6 that I bought new in 2006. I have kept a record of its fuel usage since, and I find lately that its fuel economy shows a significant drop when compared to the economy (both in town driving and open road cruising) that it gave me two years ago.

The car has done already 94000km and has always received the prescribed dealer services while still under warranty. What can I do to improve the fuel economy? - James


ON MODERN cars with fuel injection and electronic engine management, there isn't much one can do to the engine to improve fuel economy.

The combustion process will be finely regulated for high efficiency and I certainly will not recommend any alteration to the ECU settings or the fitting of any miracle gadgets.

I presume you have made sure the air filter isn't partially blocked and the oxygen sensor is operating correctly. (To check the oxygen sensor you need sophisticated equipment, so this should be done at a workshop, preferably an official VW workshop.)

There are other sensors which, when they malfunction, can dupe the on-board computer to supply an overly rich mixture. So you might as well ask the workshop to check the operation of all sensors.

I also take it you have tried raising the tyre pressures by, say, 20 kPa - this sometimes makes a surprising difference to fuel consumption without any adverse effect on ride quality or tyre life.

I think you will find that the biggest improvement in fuel economy can be achieved by analysing your driving habits. I am not suggesting that you are a bad driver. This statement is universally true for all drivers.

Try to see if you can't be smoother and gentler on the throttle without becoming a pain in the neck for other drivers in traffic. Every time you accelerate, the fuel mixture is enriched to give more power and every time you brake, some of the kinetic energy which you have built up by using precious fuel is converted to useless, unwanted heat at the brakes.

Anticipate traffic situations in time to make small, smooth adjustments to the throttle. On the freeway, try cruising at 100kmh instead of 120. It's less stressful, and safer, in addition to being more economical. If you have to endure congested city traffic every day, try to experiment with different routes and different times, if possible.

On downhill sections of city roads you can coast to a stop at traffic lights - on a fuel injected engine the fuel supply to the cylinders is cut almost completely off when the car is coasting in gear with the ignition on. If your car has a fuel economy gauge, you can learn a lot about economical driving habits by watching that.