Fuel-efficient petrol, hybrid and electric cars

Fed up with high petrol prices? A hybrid or electric car might be one answer.
 
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01 .Introduction

Hybrid-car2-iStock-sep12

We test-drove some of the currently available models in Australia and found there's a lot to like and very little not to like about these high-tech cars.

  • The fuel-efficient petrol, hybrid and electric cars available in Australia are easy to drive and use less fuel than comparable conventional models.
  • They’re all more expensive than their equivalent petrol-only non-efficient variants, so you’ll have to drive them for many years before you recover the difference.
  • They conserve oil resources and emit less air pollution and greenhouse gases.

Models tested

What's a fuel efficient petrol car?

There are a number of technologies used by car manufacturers to make their cars more efficient without resorting to battery technology. Usually a car manufacturer will release their version of an energy efficient car with a couple of different technologies such as;

  • Guidance mechanisms for more efficient gear changing by the driver, 
  • Automatic gearing that makes the best use of gear ratio,
  • An engine off mechanism, where it turns off the engine when the car stops at lights,
  • Braking systems that feeds energy back into the car battery,
  • Low profile tyres to make it more efficient for rolling resistance,
  • Lighter body weight, meaning better fuel efficiency, for example removing the spare tyre and using lighter materials in body construction,
  • Engine construction using lighter materials and more efficient engines.

Examples include the Mazda SkyActiv and VW BlueMotion technologies.

What's a hybrid?

There are a few differing examples of hybrid technologies in the market place these days. What they all have in common is battery technology working with a petrol engine. What differentiates them is how they work together. There are three main technologies out at the moment;

A system where the electric engine can power the car on its own such as the Toyota Prius, Camry and Prius C, also called a power split or series parallel hybrid,

The system where the electric engine is designed to assist the petrol engine when it's moving, such as the Honda Civic Hybrid, CR-Z and Insight, also called a parallel hybrid.

Finally a system which is designed to mostly run on the battery and the petrol engine is designed to recharge the battery, also called a series hybrid. There are no examples of this commercially available in Australia at the release of this story.

There are also plug-in hybrids which can supplement energy generation by supplying it from the power grid however these are not yet common within Australia. Questions arise whether these are really green options are dependent on where the car owner sources their electricity (coal fired or a green energy source).

What's an electric car?

A simpler explanation than hybrid, this is an electric vehicle that is powered by an electric engine and battery. Recently introduced in Australia, there is a very slow uptake of these types of vehicles due to;

  • Higher purchase price compared to petrol engine, 
  • Range anxiety (shorter distance capacity), 
  • Lack of recharging infrastructure compared to petrol stations,
  • Battery replacement cost.

A number of these reasons will reduce over time such as infrastructure build up and the lowering of battery prices as manufacture increases. With better battery technology range anxiety ought to decrease and if electric cars become more mainstream their price will become more competitive with the petrol car. There are a few examples of electric cars in Australia at present such as the Mitsubishi i-Miev and Nissan Leaf. There are others slated for release in future.

A current advantage of electric car is the lack of moving parts compared to a petrol engine vehicle, which make servicing the car presumably more cost-effective.

 
 

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02.Economy and emissions

 

Fuel economy

In tests carried out for the Australian Green Vehicle Guide, the fuel consumption in the standard combined city/highway test cycle for the Prius was just 3.9 L/100 km, for the Civic 4.4 L/100 km.

Size-wise (not engine-wise; the point of hybrids is that they have smaller petrol engines), Toyota compares the Prius to its regular Camry, the automatic 2.5 L version of which uses 7.8 L/100 km. The closest non-hybrid Honda Civic is the manual Si sedan, which uses 6.9 L/100 km .

Petrol is not (yet) quite expensive enough to make a hybrid the accountant's vehicle of choice. At $1.50/L of petrol, and based on travelling 15,000 km/year and the above consumption figures, it'll take many years to gain back the difference in purchase prices between the base Prius and the Camry, ditto for the Honda. At potentially higher prices it would drop substantially.

It's worth noting that for all cars the standard test cycle often gives numbers that are hard to match in the real world. In real life you can probably expect the consumption to be a litre or so higher - which is also what we roughly saw on the fuel economy in cars we’ve reviewed. Drivers can monitor economy as they go, and take up the challenge of equalling the published numbers - for example, by not accelerating too hard.

Emissions

All hybrids emit less greenhouse gas than most standard petrol cars. The main greenhouse gas from cars is carbon dioxide, which is directly related to the amount of fuel used. An Australian study that included the Prius and some experimental hybrids estimated a 66% reduction in carbon dioxide emissions compared to the average Australian family car. 

The Green Vehicle Guide rates the Prius at 9 (out of 10) for greenhouse emissions and the Civic Hybrid at 8.5. As a comparison, the non-hybrid Civic rates 7, the Camry 6.5.

When it comes to electric vehicles, the big advantage for emissions-conscious drivers is the lack of emissions at the non-existent tailpipe. As noted earlier however, this assessment really depends on where the driver is sourcing their electricity for the batteries that power the engine.