About what we tested to find out what really improves fuel mileage

The car industry has linked buying new cars, which are undoubtedly more fuel efficient, to saving fuel and being 'greener'. But for most people the concept of spending $20,000+ to start saving money on fuel is, frankly, ridiculous. 

Yet there is plenty that ordinary motorists can do to save money on fuel, emit less CO2 and generally consume less - which will be increasingly important to Australia's energy security in the very near future.

Simply driving differently is certainly not as sexy as buying one of the first batch of Camry hybrids due out of Altona soon, nor as simple as fitting a 'miracle' fuel saver, but it works, and you can do it now. 

If, instead of giving Toyota (the largest car company on earth) $70 million in taxpayer funds to build the Camry Hybrid, Australian governments educated ordinary drivers how to drive more efficiently, a 10 per cent reduction in national fuel consumption would be achievable.

This would cut greenhouse emissions by more than four billion kilos, and return around $200 annually to struggling families in direct savings. We would also need to buy almost three billion litres less fuel (petrol and diesel). It's worth remembering that the crude oil used to make that fuel originates generally in despotic regimes that hate the west - so there's a major macroeconomic benefit to be enjoyed as well.

Look at it another way, cutting 10 per cent from your fuel consumption is effectively the same as buying petrol for almost 15 cents a litre off the current price. Significantly better than a shopper docket. 

The Federal Government on one hand offers public information in the Green Vehicle Guide on consumption-cutting. It includes: “use air conditioning sparingly”. Right. Tell that to a Brisbane-based sales rep any time in January. On the other hand of course, the Federal Government reaps 38-cents of fuel excise (plus GST, thanks very much: a tax on a tax) from each of the almost 20 billion litres of unleaded petrol our nation consumes annually – that’s a $7 billion annual revenue stream for the nation’s treasury; rather a large potential conflict of interest.

The good news is that two small but significant changes to the way you use your car might mean a worthwhile cut in your personal fuel consumption. This can save each driver a little money individually, but it’s also worth remembering every kilo of petrol (1.4 litres) you manage to wipe from your fuel consumption slate also represents a consequential reduction of around three kilos of carbon-dioxide emission. Cutting consumption is a benefit both economically and environmentally.


Global Green Challenge-winning Hyundai Santa Fe SUV achieved 5.2L/100kmThese tests were conducted in mid-2008 by motoring expert John Cadogan - an engineer and a journalist. Cadogan won the production car class of the 2007 World Solar Challenge (a fuel economy race for production cars stretching for 3200km from Darwin to Adelaide). He also later went on to win the SUV class of the same event in 2009 (which was re-named the Global Green Challenge) with multiple Australian rally champion Ed Ordynski.

We took one Calais V V6 (the multi-point fuel injection on that pre-dated the newer SIDI direct injection engine introduced in 2009) and one chaotic Sydney road system. We used the same pieces of road for the same tests, drove in the same direction (to negate the impact of a net gain or loss in altitude), at the same times of day and in the same basic traffic density, and as far as possible varied only the condition under the microscope.

The VE Calais V V6 at the time boasted the most popular drivetrain in Australia’s most popular car, but the main reason we chose it was the trip computer. Its ‘fuel used’ function goes off and asks the engine control computer how much fuel the injectors are consuming – a precisely known quantity.

It meant we could test accurately and directly how much fuel was being drunk without resorting to the inherent inaccuracy of parking at the same bowser at the same filling station, and going through some frankly inexact fuelling protocol such as the second click at the pump nozzle, or visually sighting the fuel in the filler neck. Filling a fuel tank repeatably is a very inexact process in the real world.

With the Calais we didn’t have to drive tens of thousands of kilometres to derive meaningful results, and we were able to isolate and assess only the driving conditions under evaluation, and not the transit between the tests to the petrol station.

The Calais presents its 'fuel used' readout in increments of 10ml, meaning measurement accuracy better than one per cent provided each test consumed more than one paltry litre of petrol.

fuelJohn Cadogan1 Comment