THE continuous rise in oil prices have forced drivers to focus more attention on fuel efficiency and car manufacturers have been working overtime to try and squeeze more out of a litre of fuel as this is becoming a major selling point for drivers.

Unfortunately there is one fact that has been working against innovative car manufacturers — the trusted internal combustion engine (ICE) is notoriously inefficient. Typically the mechanical energy that is produced by an engine is about 20 per cent of the energy contained in the fuel, most of the energy from a car’s engine goes out the tail pipe and the radiator as heat.

Furthermore, engines have to be connected to some form of transmission — a differential — to get the power to the road, and all these mechanisms use energy.

While engine design has essentially remained the same since it was first invented, the systems that manage the engines have changed radically with the development of computers.

This is where most of the efficiency gains have been derived. Modern car engines are managed by very advanced computers systems.

Transmissions, for instance, have seen major changes since the invention of the manual gearbox.

There is now a choice of the traditional manual transmission (MT), the traditional automatic transmission (AT), Continuously Variable Transmission (CVT), and Direct Shift Gearbox (DSG).

Newer systems such as the CVT now used in most JDM (Japanese Domestic Market) cars and DSG transmissions, used by many VW and other European cars, offer significant efficiency and performance gains over older transmissions.

Fuel economy of JDM cars is usually expressed in kilometres per litre (km/l). This can be converted to miles per US gallon (MPG) by multiplying by 2.33. European car fuel economy is usually expressed as Litres per 100 Km (L/100km), note that with L/100km a higher figure is bad and lower figure is good, the opposite to what we are used to with MPG.

The accompanying chart shows a list of popular JDM cars and the stated fuel economy. This information is taken from the Japanese automotive guidebook 2008 where fuel economy is measured using the 10-15 method. This method of testing is done on a dynamometer under controlled conditions to ensure repeatability and proper comparison of cars. The simulated tests include a mix of city, highway and stop and go-driving,

A careful look at the list will show that the more efficient cars are generally lighter with smaller engines and use CVT transmissions. At the top of the list is the Honda Fit with 24 km/l or 56 mpg, followed by the CVT equipped Mazda Demio, note the difference between the Mazda Demio equipped with CVT and AT transmissions. Demonstrating the superior efficiency of CVT and hence its increased popularity.

The km/l figures given is excellent for comparing efficiencies of cars however, actual fuel economy in real-life driving situations will vary depending on several factors, including driving conditions, driving styles, age of car, service status of car. In addition, a car which does primarily highway driving may give better Km/L than one spending more time on busy city streets. Also a driver with a ‘heavy’ right foot will see lower figures than his ‘light-footed’ friend.

Bigger cars and SUV offer lower fuel economy and drivers should take these into consideration when changing their vehicles. Many JDM cars now come equipped with fuel economy gauges on the dash board, so drivers can see how they are consuming fuel, the beauty of these gauges is that you can adjust your driving styles and immediately see the effects on fuel consumption. These gauges typically give instantaneous Km/L and average Km/L.

Andrew Jackson is CEO of used car dealership Jetcon Corporation and past president of the Jamaica Used Car Dealers Association. The views expressed do not reflect those of the JUCDA. Visit our Facebook page “https://www.facebook.com/jetconcars”