Fuel consumption labels - fact or fiction?

Bought a new car lately? Is it using more fuel than the label on the windscreen says it should? That's not surprising.

A study commissioned by the federal Department of Environment and Heritage has concluded that the official tests which measure the emissions and fuel consumption of new cars are not an accurate reflection of today's real world driving conditions in Australian cities.

The study has devised a tougher emissions test, based on actual driving patterns, road types and traffic conditions in our urban areas, which is currently being trialled by the Department of Transport on 35 popular new cars, to see if it also provides more accurate fuel consumption figures than those currently given to new car buyers.

The preliminary findings of the second National In-Service Emission (NISE2) study also cast doubt on the accuracy of the emissions and fuel consumption figures currently shown on the fuel consumption label, which since 2004 has been a compulsory fixture on the windscreen of all new cars.

New car buyers "need to be cautious in believing that the consumption shown on the label is what they'll actually get," says Jon Real from the federal Department of Transport and Regional Services (DOTARS).

"We've had feedback from people saying that the fuel consumption figure on the label is unrealistic," he said.

The fuel consumption label was introduced to promote consumer demand for more environmentally friendly vehicles. It is an integral part of the federal government's National Greenhouse Strategy; its importance has further increased in the past 18 months as spiralling petrol prices have caused many new car buyers to take a closer look at how consumption rates of different models compare.

These tests are done in laboratories, not on the road. The car makers themselves conduct the tests and supply the figures to the federal departments of transport and environment.

The pre-2003 fuel consumption test - part of the Australian Standard AS2877 - on which manufacturers based their fuel economy claims was itself discredited because its results, especially those quoted for city driving, were wildly optimistic and almost impossible to achieve in the real world.

Australia adopted the European emissions standard/fuel consumption regime, the UN ECE Type 1 test, in 2003. It's now part of Australian Design Rule (ADR) 79/01; the fuel consumption component, including the label, is incorporated in ADR 81/01.

These tests are done in laboratories, not on the road. The car makers themselves conduct the tests and supply the figures to the federal departments of transport and environment.

Part of the problem is the fact that Australian consumers are not given a city/country breakdown of the test results. Manufacturers and importers are not required, under the ADRs, to make them public, even though they obtain both during their ADR tests.

In Europe, both the city and open road figures are quoted by car makers, along with a weighted average.

The actual terms used for city and country are urban and extra urban; the latter, contrary to its implied meaning, refers to highway and motorway driving, at speeds of up to 120 km/h, common in Europe.

In Britain, car makers must quote three fuel consumption figures in their advertising: urban, extra urban, plus combined. Similar regulations apply across the EU.

In Australia only a single figure average, called the combined figure, is displayed on the fuel consumption label, and quoted by car makers in their advertising and press material.

The combined consumption is calculated according to a formula weighted heavily towards the open road component of the ADR test, so it's invariably optimistic when compared with real world averages, especially for city based commuters.

If you live in Sydney, and only hit the highway a couple of times a year, the number on the fuel consumption label will always be lower than your car's actual fuel consumption, by 50 percent or more in the case of some big, heavy cars or 4WDs with large capacity petrol engines.

The averaging formula makes these vehicles look particularly frugal because the discrepancy between their city and open road consumption rates is much greater than in smaller, lighter four cylinder cars.

Take the BF Fairmont Ghia six speed automatic, for example. Ford has made much of its improved fuel consumption figures compared with the four speed BA Falcon.

Ford quotes an ADR81/01 average of just 10.2 litres/100 km, with the BF's 190 kW 4.0 straight six running on 95 octane petrol - impressive, and a claimed 11.3 percent improvement over the 182 kW/four speed auto BA.

If you live in Sydney, and only hit the highway a couple of times a year, the number on the fuel consumption label will always be lower than your car´s actual fuel consumption, by 50 percent or more in the case of some big, heavy cars or 4WDs.

However, the urban test cycle figure for the five speed automatic variant is 13.8 litres/100 km - hardly what you would call economical four cylinder motoring and nearly 4 litres/100 km higher than the combined average shown on the windscreen label.

On the highway, where the Camry's 2.2 litre four cylinder engine does not have to repeatedly move its large mass from rest, and it has the advantage of a tall fifth gear, it returns just 7.7 litres/100 km.

Bear in mind that how you drive and where you drive will also affect consumption - again, the differences between city/ country, and the real world/ADR combined averages, are amplified as vehicle weight and engine size increase.

The results of the NISE2 city fuel consumption test, devised by the Transport Systems Centre at the University of South Australia, will be posted on the green vehicle guide website when the tests are concluded.

The Department of Transport will also include an analysis of the discrepancies between the test results, and fuel consumption figures obtained under ADR 81/01 procedures.

An updated regulation - ADR81/02 - is currently under development, which will bring the Australian fuel consumption/emissions testing and reporting regime into line with the latest ECE 101 rules.

This means that manufacturers will have to supply the Department of Transport and Regional Services (DOTARS) with urban, extra urban and combined fuel consumption figures.

"The content and format of the fuel consumption label will be reviewed as part of the ADR81/02 process," said DOTARS' Jon Real.

"Providing urban, extra urban and combined numbers on the label, and on advertisements for new cars, is an issue we could look at," he said.

Meanwhile, if you're buying a new car and you want accurate fuel consumption numbers, ask the manufacturer, via their website or customer assistance phone number, to give you the individual urban and extra urban cycle figures, rather than relying on the label average. You'll also find real world fuel consumption figures from our road tests, at NRMA Car Reviews.

HOW THE ADR FUEL CONSUMPTION FIGURES ARE CALCULATED

The UN ECE Type 1 test, now used to collect emissions and fuel consumption data on new cars in Australia (and Europe), consists of five simulated driving cycles over a total distance of 11.023 kilometres.

The urban (city) cycle takes 195 seconds. It's performed four times. It comprises 36.9 percent of the total distance; the extra urban (highway) cycle, which takes 400 seconds, is performed once. It comprises 63.1 percent of the distance.

The single fuel consumption figure, displayed on the label, is determined by applying these distance percentages to the actual urban and extra urban consumption numbers, and adding the two for a final average.

The fact that 63.1 percent of the average is derived from the highway part of the test explains why the figure on the fuel consumption label bears little relationship to how much fuel your car will use in the city. It also explains why the gap between reality and laboratory numbers escalates in proportion to the size of the car and the capacity of its engine.

The NISE2 study test devised by the Transport Systems Centre of South Australia is also a laboratory test, but it is based on an analysis of actual driving patterns in Australian cities, using Global Positioning System (GPS) tracking of routes, speeds and traffic flows.

It's called the Australian petrol composite urban emissions drive cycle, or Petrol CUEDC. The test is a simulated 19.442 kilometre course, and takes 29.95 minutes. Four types of conditions are simulated: residential, congested, arterial and freeway.

Theoretically, it is possible to tailor this test, using the GPS data, to provide specific speed/traffic/road/geography profiles for individual state capital cities, which would give different consumption rates for the same car.

By Bill McKinnon, August 2006.