Hopes that car use will become more sustainable through better fuel economy are widespread, and often exploited for political advantage. In 2007, for example, then State Treasurer John Brumby used this myth to defend cuts to stamp duty on large new cars:

I think it is generally accepted that newer cars are certainly much cleaner, as I said, much safer and generally more fuel efficient – not all of them, but generally more fuel efficient…. I certainly believe that there will be very positive environmental benefits from getting people out of old [cars]…. and getting them into new cars.

—John Brumby, Victorian Hansard, May 2007

Such hopes have been likened to walking down an ‘up’ escalator. Even if vehicles become on the whole more fuel efficient, motorists can be expected to respond much as they would to a drop in petrol prices: by driving further and more often.

However, there is little indication that the cars we actually drive are becoming any more fuel efficient. In Britain, the Royal Commission on Environmental Pollution found that, while the fuel economy of new British cars improved during the oil shock of the late 1970s and early 1980s, fuel economy has actually worsened since then. The official figures for Australia tell a similar story.

For many decades, the Australian Bureau of Statistics has conducted a Survey of Motor Vehicle Usage, which estimates the average fuel consumption of all Australian passenger vehicles on the road. This figure has hovered between about 11 and 12 litres per 100 km over the entire period for which data have been collected. The 2020 figure of 11.1 litres/100km, while among the lowest recorded, is only 12% less than the highest recorded figure of 12.6 l/100km in the 1970s, and barely lower than the very first figure of 11.4 l/100km collected in 1963, nearly half a century earlier!

The same ABS data tells us that in 2006 (for example), those driving cars purchased since 2000 got an average fuel efficiency of 12.1 litres per 100km, one litre higher than the average efficiency of cars purchased between 1990 and 1999, of 11.1 litres per 100km.

More recently, a 2019 study by think tank Transport Energy/Emission Research (summed up in this article from The Conversation) found that—contrary to official figures suggesting a gradual decline—the real-world CO2 emissions intensity of motor vehicles has actually been on an increasing trend since 2014.

So despite what John Brumby might say, it is clear that newer doesn’t always mean more economical.

It is likely, as transport researcher Patrick Moriarty argues, that improvements in engine efficiency over the decades have been offset by other factors: the trend toward larger vehicles such as four-wheel-drives, increased use of air conditioning, electronic control components demanding greater weight and power input, ageing of the car fleet, and compromises required to reduce air pollution.

Compounding this is the psychology of car buyers themselves. American author Tom McCarthy in Auto Mania, his 2007 history of the US car market, argues that the oil shocks of the 1970s, far from driving a trend toward greater fuel economy, actually undermined the desire for efficiency among consumers in the longer term. This is because during these oil shocks, fuel economy became associated in people’s minds with material deprivation, denial and sacrifice. Once oil prices came down in the 1980s, people could barely wait to take advantage of this with bigger and more fuel-hungry cars, through a simple urge to demonstrate their new-found control over circumstances. In Australia, we can liken this to an earlier event: Robert Menzies’ abolition of postwar petrol rationing in 1949 similarly unleashed a tide of latent demand for car travel, and the ceremonial burning of ration books that represented forced economies.

In recent years, hybrid petrol-electric vehicles hit the market amid a flurry of marketing hype that promises astounding fuel efficiencies, with ads promising that you’ll only have to visit a petrol station once a year or less. But as early as 2005, hybrids in America were starting to follow the same old trend: improvements in engine efficiency were being used not to reduce fuel consumption, but to put more ‘grunt’ under the bonnet.

Mark Buford is happy with the Honda Accord hybrid that he bought six months ago, and he has already driven it 13,000 miles. He was determined to buy a hybrid electric car, he said, and this one is clean, ‘green’ and accelerates faster than the nonhybrid version. He just cannot count on it to save much gasoline.

….Hybrid technology, it seems, is being used in much the same way as earlier under-the-hood innovations that increased gasoline efficiency: to satisfy the American appetite for acceleration and bulk….

Consumer Reports, in an article published in May, found that in actual on-the-road conditions the Accord hybrid averaged 25 [miles per gallon], versus 24 m.p.g. for the 4-cylinder model and 23 m.p.g. for the nonhybrid V-6….If every car in the country were converted to a hybrid with that improved mileage, the gain would be swallowed up in three to four years by growth in driving demand.

—Hybrid Cars Burning Gas in the Drive for Power, New York Times, 17 July 2005

Sure enough, subsequent industry reports showed the Australian hybrid car market falling in with the American pattern, even as (or indeed because) it became more attractive to ‘mainstream’ consumers:

At the launch of the new-generation Toyota Prius in Sydney yesterday, chief engineer Akihiko Otsuka admitted the company had opted for a bigger, more powerful engine because customers had demanded it…. With a different approach, we could have done even better. However, customers told us they wanted more performance. In response, we selected a larger engine.

—Prius a paler shade of green, The Age, 7 July 2009

Hybrid or not, with each passing decade our cars have increased steadily in weight and engine power in line with improvements in engine technology. After all, what new car buyer can resist a bigger and more powerful car that costs the same to run as their previous vehicle?

The modern ‘equivalents’ of all three small cars I used to drive (Fiat 500, Suzuki Swift and Mini-Minor) are each fully twice as heavy as the older ones. This is despite their using modern, lighter construction methods. A lot of the mass is in needlessly-bigger engines, power windows, power steering, power brakes, powerful sound systems and other luxury equipment. The 4WDs are even worse with the Toyota Land Cruiser, Land Rover and Nissan Patrol each having grown from 2.2 to 2.5 and now 2.7 tonnes over the past two major model changes.

—John Harland, Going Solar Transport Newsletter, 15 September 2008

From 1980 to 2004 the average fuel economy of the US new passenger automobile fleet increased by less than 6.5 percent. During this time, the average horsepower of new passenger cars increased by 80 percent, while the average curb weight increased by 12 percent. Changes in light duty trucks have been even more pronounced. Average horsepower increased by 99 percent and average weight increased by 26 percent from 1984 to 2004. The change within passenger cars and light trucks hides much of the story. In 1980 light trucks sales were roughly 20 percent of total passenger vehicles sales; in 2004, they were over 51 percent.

—Christopher Knittel (Institute of Transportation Studies, University of California), Automobiles on Steroids, 2009

As cars became more efficient, people began buying larger, heavier and more powerful cars. In particular, we got hooked on sport utility vehicles and those formless blobs on wheels known as crossovers, which became one of the hottest segments of the car business. A decade ago, about half of all cars sold were sedans, which are some of the most efficient vehicles on the road, and about a quarter were S.U.V.s, which are some of the least efficient. By 2019 only a third of cars sold were sedans, and about half were small or large S.U.V.s. Given more efficient cars, we bought more car….

The growing adoption of electric vehicles over the last decade did little to counteract these larger forces; any environmental benefits we got from zero-emission E.V.s were swamped by the much larger market shift toward bigger cars.

—Farhad Manjoo, “There’s one big problem with electric cars“, The New York Times, 18 February 2021

This is also why glowing reports of new hi-tech ‘ultra-efficient’ cars like this one are of little relevance to the urban transport problem (at least until petrol is much more expensive than it is now). Quite simply, the factors that make these vehicles highly efficient also make them less attractive to the typical motorist. The world record for vehicle fuel efficiency has already been set for all time by the bicycle, which has infinite efficiency since it requires no fuel at all. A motorist who wishes to maximise their fuel efficiency would be well advised to just switch to cycling. On the other hand, a motorist who finds riding a bike unattractive is unlikely to be attracted to these ultra-efficient vehicles for much the same reasons.

It’s extraordinary that we have this sense that somehow or other all we have to do is make slightly more efficient cars and everything will be fine on the transport front.

—Professor Peter Newman, The Australian, 19 September 2008

In Victoria, the idea that people would suddenly buck all historical trends and embrace vastly more efficient cars, thereby slashing transport emissions, achieved a new prominence in 2008 with the release of two reports by management consultants the Nous Group. These reports put forward scenarios for achieving big cuts in Victoria’s greenhouse emissions, and in transport, the biggest cut was said to be achievable though improved fuel efficiency. One of these reports was produced for Environment Victoria, and helped strengthen the belief even among some environmentalists that it is more important to pursue improvements in car technology than to seek better public transport.

To obtain their conclusion, the Nous consultants blithely assumed a wildly optimistic reduction in fuel consumption of 30% between 2010 and 2022, increasing to a 60% reduction by 2030. Not only is such a reduction utterly without precedent, including in the oil shocks of the 1970s: according to analysis by the Bus Association of Victoria, it would have required every new car purchased from 2010 onwards to be as efficient as a Toyota Prius! (As of 2018, total fuel consumption by motor vehicles in Australia had actually shown a 9.6% increase since 2010.)

Policymakers and their consultants such as Nous had, at least until recently, been seduced by the idea that cars only use as much fuel as they do because of insufficient take-up of new technology, and there is a huge ‘free lunch’ to be had simply from decreeing tough new efficiency standards. Vehicle efficiency improvements in Europe were held up as an example. In fact the biggest factor leading to real improvements there – the trend toward smaller vehicles and the bucking of the trend toward larger vehicles elsewhere – long predated the development of aggressive standards, and arguably helped make those standards politically palatable. This Europe-specific trend owes as much to Europe’s high fuel prices, greater respect and provision for public and non-motorised transport, and closer settlement patterns as to any other factor.

As we now know, much of the efficiency gains and emissions reductions claimed for those European standards were illusory. The first clue came in a 2012 report to the European Commission, which pointed out that about a third of the ‘registered’ CO₂ emission reductions from new cars between 2002 and 2010 had not actually occurred. It appeared instead that flawed test procedures and ‘flexibilities’ in those procedures had been exploited by carmakers to produce ‘laboratory’ fuel efficiency figures about 30% more optimistic than drivers will achieve in reality.

From these numbers it can be concluded that it is likely that in the period 2002-2010 the registered CO₂ reduction of passenger cars [by 26.8g/km] has to a large extent been caused by implementation of technology, but also that the assessment made here reveals a gap of around 9g/km that cannot be attributed to technology deployment…. The estimate of the potential impact of test procedure flexibilities and their level of utilisation in the 2002-10 period appears to explain the remaining gap.

—Supporting Analysis regarding Test Procedure Flexibilities and Technology Deployment for Review of the Light Duty Vehicle CO2 Regulations, page 10

It’s clear that around a third to half of the fuel economy claimed by car makers is just hot air. Car buyers are being cheated by the makers manipulating test results to achieve better fuel economy than is possible on the road. Policy makers are being cheated as regulations intended to improve efficiency are only being met in the laboratory. And the environment suffers as official statistics indicating action to reduce greenhouse gases turn out to be greatly exaggerated.

—Greg Archer, Transport and Environment, January 2013

But the true extent of this “cheating” only became evident in 2015 when Volkswagen admitted that for years it had incorporated technology into its diesel cars to detect when an emissions test was being carried out and switch to a less polluting low-performance mode. It soon became evident that not only Volkswagen but a long list of other major manufacturers of supposedly ‘efficient’ diesel-engined cars had been using technological tweaks to ‘defeat’ emissions tests.

As technology writer Mike Barnard pointed out, conventional car technology has already reached the point where any further ‘free lunch’, no-regrets benefits simply do not exist.

The VW scandal is just making public what a lot of people already knew: it isn’t possible to make gasoline or diesel engines significantly better in the compromise space between CO2 emissions, NOx and other pollutant emissions, mileage, performance, and engine longevity. That road, amazing as it has been, has reached its end.

—Mike Barnard, CleanTechnica, 17 October 2015

As Barnard states, battery-electric vehicles show some promise of further efficiency improvements over the current fleet. This still relies on getting our electricity in future from renewable sources rather than fossil-fuelled power stations, which themselves are scarcely more efficient or less polluting per unit of energy than the current petrol or diesel-fuelled vehicle fleet.

As we emphasise in our discussion of car pooling, emissions reduction forecasts and other such figures are little better than random numbers unless they compare achievable outcomes in one area with what is achievable in another area with the same effort. Big gains in public transport patronage have been shown to be achievable: similar big gains in the efficiency of the national car fleet have not, either in the past or today. Recall that to the Federal Government in 2009, ‘green motoring’ simply meant reducing the Commodore’s fuel use from 10.6 to 9.3 litres per 100km. A 2013 report from the US National Academy of Sciences emphasises that technology alone will not suffice to cut energy use and emissions by the amount required in a low-carbon future.

As Paul Mees concludes:

Per capita travel by car by residents of Australian cities doubled between the early 1960s and mid-1990s, and so did the urban population. The ‘up’ escalator of travel growth has run at high speed, while the downward effect of improved technology has been nonexistent.

—Mees, A Very Public Solution, p.61

Or, as a Canadian journalist summed it up:

I don’t need to run out and buy a hybrid car out of guilt…. I can certainly hang up the keys more often and probably achieve the same effect.

—Lorraine Sommerfeld, Hamilton Spectator (Canada), April 2007

Last modified: 10 October 2021