Consumption rates

Unless you happen to have an oil well in the backyard, you're probably giving the issue of fuel economy some serious consideration, particularly if you're about to buy a new car. The more expensive fuel becomes, the more you stand to save by choosing an economical car.

And the more fuel efficient your car is, the greater your contribution to the amelioration of the greenhouse effect, because every litre of fuel burned produces about 2.3kg of carbon dioxide, the main greenhouse gas.

Big heavy cars use more fuel than small light ones, which is the main reason why two tonnes plus petrol powered 4WD wagons occupy the thirsty end of the consumption spectrum - and some now cost $150 or more to fill up - while 900kg runabouts can still deliver a week's worth of mobility for $30.

The tiddlers - Toyota's Yaris, Hyundai's Getz, the Honda Jazz and other 1.3-1.5 litre small cars - can return 7-8 litres/100km in city driving, on regular unleaded. On the highway, though, their engines have to work just as hard keeping the plot rolling along at 100km/h, so there'll be little or no improvement.

The next size up - Holden Astra, Mazda3 and the rest, with 1.8-2.0 litre engines - will generally return 10 litres/100km or better in town, though if you go for an automatic this may rise to 12 litres/100km or so. On the open road, expect to use less than 8 litres/100km.

It pays to check in this class (and others) whether the cars' engine is designed for 91 octane regular, 95 octane premium, or 98 octane premium unleaded, because 91 octane is much cheaper.

The manufacturer's recommendation, contained in the handbook, is the key. Some cars will run on the full range of fuels. If 91 octane is recommended, you're wasting your money using the more expensive stuff. Others, such as VW's Golf, specify 95 octane as the minimum and prefer 98 octane, which in some areas can be difficult to find.
 
Medium sized four cylinder cars like Toyota's Camry, Mazda6 and the Honda Accord will usually consume 10-12 litres/100 km in town, and 7-9 litres/100 km on the highway, where the longer legs of their larger capacity engines come into play.

The same goes for the Falcon and Commodore. While their city fuel consumption numbers average about 14-17 litres/100km (on regular unleaded), the open road sees their high torque/tall gearing drivetrains able, in the Commodore's case, to do 8-9 litres/100 km.

Ford's Falcon does 10-11 with the four speed auto; the new six speed, available in the BF, produces similar highway economy to the Commodore.

Among the luxury brands, BMW's attention to minimising weight and maximising fuel efficiency is evident in impressive economy from its four and six cylinder engines in the new 3 Series and the 5 Series. Mercedes-Benz also does some low numbers in its new A Class and the C200K. 

A four-wheel drive can either send you broke or be a surprisingly economical proposition. Anything with a large capacity ' say 4.0 litres or greater ' petrol engine in it will be expensive to run. Expect 20 litres/100km in town, more if you're careless and 12-14 litres/100km on the highway.

Big V8 powered 4WD wagons like the Range Rover and Jeep Grand Cherokee can use 25 litres/100km in town. That's twice as much as many cars.

Toyota's 4.0 litre petrol engine in the Prado, though, is pretty good, returning Falcon like numbers with the new five speed auto. The 3.3 litre Kluger (and its Lexus RX330 counterpart) are also at the economical end (15-17 litres/100km in town) of this class.

Given the fact that diesel is often ten cents per litre more than regular unleaded, its value for money case is still rather problematic in many cars, but in 4WD territory diesel wins every time. A large diesel 4WD like the Hyundai Terracan CRDi, Land Rover Discovery or BMW X5 can use 8-9 litres/100km on the open road, and less than 13 litres/100km in town.

If you're looking for a high tech, fuel efficient, clean, green family car, it's pretty hard to go past the Toyota Prius petrol/electric hybrid. It's a spacious, comfortable sedan, with a five star crash test rating, all the equipment you need and the ability to get around town using just 5.6 litres/100km of regular unleaded. Honda's Civic hybrid, a smaller sedan, returns similar figures.

In the short term, expect to see more hybrids. Lexus will introduce two new ones here in 2006. The RX400h is a hybrid powered version of the RX SUV wagon, while the GS450h is a hybrid luxury car.
 

Article by Bill McKinnon, October 2005