Easy on the gas: Making vehicles more fuel-efficient

By ALASTAIR SLOANE

New Zealanders are largely philosophical about the increased cost of petrol and diesel. There is nothing they can do about it. Other people are to blame. It is cyclical, the price will come down again, they say.

There is none of the panic of the fuel crisis in the 1970s, when the country queued for petrol and carless days were introduced.

Carmakers aren't rushing out special fuel-frugal models, like Holden did all those years ago with the four-cylinder Commodore. It could be as thirsty as the six-cylinder.

Engine technology is the best it's been. Driven wisely, four-cylinder engines can return excellent fuel figures. So can sixes. Even a thumping great V8 can be coaxed into producing more for less.

Colossal sums of money are going into research on how to replace the internal combustion engine with powerplants that do not depend on petroleum.

DaimlerChrysler's latest alternative fuel model is based on the A-Class and was unveiled in Germany this week. It is called the Necar 5 and uses a methanol-powered hydrogen fuel-cell. The company says the car has a top speed of 150 km/h and will be available for sale in 2004.

Ford is spending more than $2 billion to put a family car that runs on hydrogen on the road by 2004. General Motors will also put a hydrogen fuel cell vehicle into production.

But chairman Jack Smith said huge challenges remained before a substantial shift to hydrogen-powered transport could be achieved.

"The long-term potential is great and we are making good technical progress ... but huge challenges remain in the three critical areas of cost, technology and infrastructure," he said.

"The costs of this kind of propulsion system are very high relative to conventional engines. At this point, it appears that a substantial switch to hydrogen could occur only over a period of decades."

Hybrid models like the Toyota Prius and Honda Insight will make their way into the mass market before hydogen. Both cars are being trialled in New Zealand.

The Prius uses a 1.5-litre four-cylinder petrol engine and an electric motor. At slow speeds electricity drives the car; at higher speeds the engine takes over. It's a Scrooge at the petrol pumps, capable of 80 mpg, or under 3-litres of fuel for every 100km. But it would cost about $50,000.

Meantime, motorists can take a few steps to reduce the impact of increased fuel costs.

"The answer is to use the smallest, most modern vehicle you can, keep it properly tuned, choose your routes effectively, use it only when necessary and drive in a fuel-efficient manner," says Mazda's former technical chief Roger Russell, now an executive with emergency group First Assistance and Rescue.

"The weight and size of a vehicle are crucial. A heavy vehicle takes more energy to move and more fuel must be burned. In testing, we have measured a decrease in fuel consumption by just removing the spare tyre.

"Choose the most modern vehicle possible to take advantage of the latest engine technology and vehicle aerodynamics. In this case the oldies are not the goodies."

The vehicle must be kept tuned. "Remember service checks. A worn set of sparkplugs or an overdue air filter can increase fuel consumption by between 15 and 30 per cent."

Tyres should also be inflated to the highest pressure recommended by the manufacturer. This will not only save fuel but improve the vehicle's handling and extend tyre life. Tyre pressures should be checked only when the tyres are cold.

Maps are cheaper than petrol. Choosing routes poorly can gobble up fuel. Sitting at lights or in queues of traffic is wasteful. So are short trips from cold starts.

Then there is driving style, which can have a huge effect on fuel consumption.

In tests, some drivers have used 50 per cent more fuel in the same car and over the same route than skilful drivers.

"Fluttering or pumping the accelerator are habits that kill fuel consumption. Jerky driving, poor use of gears and failing to match the flow of traffic are all prime causes of extra fuel use."

What makes modern cars more efficient? "The latest Mazdas, for example, use between 20 and 40 per cent less fuel than equivalent models 25 years ago," said Russell.

"Less power is wasted inside engines. Parts are smaller, lighter and machined more accurately with better surface finish. Cooling systems, transmissions and tyres waste less energy.

"Enhanced aerodynamics cut wind resistance and drag. Improved engine durability helps engines to stay tuned longer.

"The use of energy-conserving oils that match engine characteristics and are formulated to reduce drag also contribute, especially in the critical starting period when fuel consumption is at its highest."

How to calculate fuel consumption:

Start with a full tank of petrol and set the trip meter on your car to zero.

At the next fill, note the distance travelled and the amount of fuel needed to fill up again. Reset the trip meter to zero.

To work out how much fuel your car is using over every 100km, divide the litres used by the kilometres travelled. For example, if you have used 46.6 litres of petrol over 535km, divide 46.6 by 5.35. The answer is 8.71 litres for every 100km.

To convert litres/100km into miles per gallon, divide the mathematical constant 282.48 by, in this case, 8.71. The answer is 32.43 mpg. Conversely, dividing 282.48 by 32.43 gets you back to 8.71. Fun, isn't it?