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With fuel prices hitting decade lows in recent times, there has arguably never been a worse time to buy an economy-focused car.

But that doesn’t mean there aren’t some great options out there for people who are thinking about long-term sustainability and doing their bit for the environment.

As such, we’ve assembled four of the most economical-but-still-somewhat-fossil-fuel-reliant models on the market – the first-ever Audi A3 e-tron plug-in hybrid, the city-focused BMW i3 range-extender (it’s an electric car, but has a petrol engine to help it keep going), all-new Citroen C4 Cactus diesel and the icon of the green car age, the Toyota Prius petrol-electric hybrid.

These four vehicles all take different approaches to achieving the best possible fuel consumption, and this two-part test aims to establish which is the true economy winner. Yep, there’ll be two parts – this first section focuses on the urban environment, while part two will look at highway motoring, which is sure to throw a few curve balls.

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That’s because there are vast differences in the technology on offer in each of these four vehicles, and the majority of the vehicles here are aimed primarily at urban dwellers. So, some are clearly at an advantage doing the commute thing, while others are better suited to long stretches of blacktop.

We’re not talking about a hyper-miler challenge here. We wanted to see what real-world buyers and real-world drivers could expect if they were to shell out their cash for a car that claims to be ultra-economical.

Let’s take a closer look at how they stack up.

Specifications and drivetrain details

Four cars, four extremely different drivetrains, all with extraordinary claimed fuel consumption: that’s the run-down for the competitors in this eco-test.

Let’s start at the most frugal, based on each car’s Australian Design Rule fuel use claim.

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The BMW i3 range-extender model is said to use just 0.6 litres of fuel per 100 kilometres. That’s ridiculously low – but if you think about it, it is a false economy because it won’t ever achieve that little if you try to drive more than a couple of hundred kilometres.

The reason being is that the i3 has a total claimed range of 300 kilometres, though the conditions would have to be absolutely ideal to reach that level.

The battery alone is claimed to offer 150km of range, while a 0.6-litre, two-cylinder petrol engine kicks in when the batteries start to get low to offer a maximum claimed range of 300km. The petrol engine never drives the wheels – instead, it acts like a generator, using fuel from its on-board 9.5-litre tank to keep charge up to the batteries. Ah, yeah, the fuel tank is that small, so there’s a chance you could fill up for less than $10!

The battery back has 18.8kWh of usable capacity, with the electric motor pushing out 125kW of power and 250Nm of torque. According to BMW the i3 can be recharged to 80 per cent in as little as three hours if you have rapid charging availability, but the average household will likely need to leave the car overnight to get a full charge. In fact, it’ll have to be a long night, because using the standard cable in a standard outlet, you’re looking at 11 hours to get to 80 per cent.

The i3 is the smallest, yet dearest, car on test. It costs $69,900 plus on-road costs for the range-extender model. There’s a cheaper ($63,900) i3 with just a pure electric drivetrain, though that car has a much shorter 160km range without the safety net of that range-extender petrol engine. BMW i3 pricing and specifications.

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The second-most frugal of our competitors is claimed to be the Audi A3 e-tron, another plug-in hybrid but this one works quite differently to its range-extender countryman.

The A3 e-tron also pairs a petrol engine to a bank of batteries and an electric motor, and the result is a claimed consumption of just 1.6L/100km. It uses more fuel if you option the larger wheels, though.

The petrol engine is a 1.4-litre four-cylinder turbo unit, producing 110kW and 250Nm. It is paired to an 8.8kWh electric drive system with 75kW/330Nm, and the maximum drivetrain output is 150kW and 350Nm. The electric motor is integrated into the six-speed dual-clutch automatic gearbox.

That’s a pretty big jump up on the i3, but it also has more weight to move – 1615 kilograms compared to the BMW’s 1315kg, because the BMW uses a lightweight and expensive carbonfibre body shell. That’s part of the reason the i3 is so expensive, and indeed it makes the A3 look like a practical bargain at $62,490 plus on-road costs.

All A3 e-tron buyers receive a wall-mounted charging dock their your house, with electricity company Origin Energy teaming with the federal government’s GreenPower program with 10,000km of accredited renewable energy displacements. That 230-volt high-output 16-amp single-phase power outlet will recharge the car in between 2.5 and 5.5 hours. Audi A3 e-tron pricing and specifications.

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Then there’s the Toyota Prius. The world has come to know this car more than any other as the poster child for efficient motoring, and this new fourth-generation model is a lot more efficient than ever before.

It uses only 3.4L/100km, which is 15 per cent less than it did in the previous-generation model. Despite the fact it has essentially carried over the same 1.8-litre petrol-electric hybrid drivetrain, it has seen big efficiency improvements to its thermal efficiency, and you can now drive at speeds up to 110km/h (previously 70km/h).

The Prius’s engine produces 72kW of power and 142Nm of torque, while the electric motor produces 53kW and 163Nm. But the total combined power output is not the sum of its parts, with max power rated at 90kW. It still has a continuously variable transmission (CVT) auto, too.

It’s by far the biggest vehicle here, though it is the second porkiest of the cars on test, at 1400kg. Toyota Prius pricing and specifications.

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The cheapest vehicle here – and thirstiest, if you could call it that – is the Citroen C4 Cactus diesel.

It is also the least technological drivetrain in this test, with a little 1.6-litre turbo diesel four-cylinder (producing 68kW and 230Nm) and a six-speed semi-automatic gearbox. It has engine-stop start, but that’s about all the engine tech it’s packing, but it manages to be so efficient because it is very light: the diesel auto weighs just 1055kg.

All that aside, the fact that this little Cactus costs just $29,990 plus on-road costs is commendable, considering that its fuel economy is rated at a miserly 3.7 litres per 100km. That makes it the most efficient five-seat vehicle on the market that doesn’t use a hybrid drivetrain.

It’s kind of fitting that the cheaper the car gets, the more fuel it is claimed to use. But the gap is a monstrous $39,910 between the coin-conscious Citroen and the big-buck BMW. Citroen C4 Cactus pricing and specifications.

As we mentioned, though, this isn’t your average comparison test.

By the numbers

According to the Green Vehicle Guide, the cars will use the following (litres per 100km):

  Urban fuel use Highway fuel use Combined fuel use
Audi A3 e-tron n/a n/a 1.6
BMW i3 4.4 n/a 0.6
Citroen C4 Cactus 3.9 3.5 3.6
Toyota Prius 3.4 3.5 3.4

As you can see, the official figures make it a little dodgy to compare them back to back. But we made it simple for ourselves.

This part of the test covered 100 kilometres of urban driving. At the end we aimed to stop and check what each car was claiming to have used over that distance. There are no lab coats here!

For the urban loop, the drivers were myself and fellow CarAdvice testers Trent Nikolic, Curt Dupriez, as well as our office manager, Marcus Sroba.

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Our loop took us from CarAdvice headquarters in McMahons Point on Sydney’s lower north shore, over the Spit Bridge, up through Seaforth towards Forestville, back over the Roseville bridge and through Willoughby and across the Sydney Harbour Bridge towards the Eastern Suburbs. After winding through Vaucluse, Bondi and Bronte, we headed through Eastgardens, Botany, Rockdale, Hurstville, Sylvania and Caringbah before we concluded our loop at Kurnell at the oil refinery. An apt way to finish up, we reckoned.

The drive

With the i3 and A3 fully charged and fully fuelled, and the Prius and Cactus both brimmed as well, we set off.

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There are some things all of us agreed on post-drive: the Prius had a harder suspension setup that we’d expected; the i3 was also pretty brittle on rougher surfaces due to its tall and skinny rims; the A3 felt like a regular A3 and probably had the best ride of the lot; and the Cactus had a gearbox that you’d either find to be liveable or you’d want to park it near the beach and throw the keys in the ocean.

Our road loop included some terrible Sydney surfaces with sharp bumps and rough edges, as well as tight turns, steep hills and stop-start traffic. It’s Sydney, after all.

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We drove in convoy, stopping only when absolutely necessary, and none of us was out to set any Sydney circumnavigation records.

We just drove the cars like normal people would, across roads that average buyers would encounter everyday, and here’s what we thought after 100km of testing. We told you this wasn’t like a regular comparison test, and we’ve made it more about each drivers impressions of the cars on the whole rather than the nit-picking full car assessment that you may be used to from us.

Audi A3 e-tron

Around town the consensus among judges was that the A3 was liveable, likeable, and certainly not languid when it came to acceleration.

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Matt Campbell:

There’s little to give away that it’s a plug-in hybrid other than the fact that its drive modes are many and varied. They are: EV (full electric); Auto (both petrol and electric available and usable depending on the conditions); Hold (petrol engine only, with batteries taken offline); Charge (petrol engine used to power car and recharge batteries). We had the cars in their most normal or automated modes for this test.

On the road you’d not be able to tell the e-tron from any other A3 from the driver’s seat (drivetrain excluded). You can feel the electric motor hauling from zero rpm, and the transition to petrol propulsion is nearly silent. This is a very refined drivetrain, and in terms of actual driving the way the A3 e-tron steers and handles bumps is very good. It feels plush, but maybe not $62K plush… If it were $50,000 it would be an easier eco-pill to swallow.

Trent Nikolic:

In my opinion, this is absolutely the easiest of this quartet to live with in terms of modern hybrid technology and daily driving duties.

It delivers a seamless transition between electric power and the petrol engine, such that you don’t even notice it happening. If you’re unable to get to a charging point, there’s no loss of drivability either, which is an important consideration for most buyers.

Electric-only range doesn’t last long enough to really match a proper electric hybrid, but the A3 will be the vehicle that is most palatable to most buyers. 

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Curt Dupriez: 

The A3 is quite the antithesis of its rivals – it looks nearly identical to any other A3, and drives like a particularly nice A3 should. It’s an utterly normal driving experience, and all the better for it.

Further, it’ll recharge its battery back so quickly and efficiently on the move, and its EV-only range is useful enough around town, that you might never need to actually plug it into a wall during ownership. Not only is it seamless switching from EV to petrol motivation and back again, it demands hardly any extra user engagement in going about its hybrid business.

Marcus Sroba:

Pulling out on to a fast flowing main road, the e-tron took off and quickly got up to speed, which reminded me just how quick the electric motors can be. As it was nearing the end of the day the charge level was low, and the Audi kept jumping between the electric and petrol motors. But honestly half the time I had no idea which one was supplying the power.

My biggest problem is it lacks the flair of others in this category. It needs some wild lights or funky interior or even so air bubbles but I suppose that will be the reason most people will buy it. There’s nothing whacky on the outside, nothing whacky on the inside. It’s a normal car to look at and sit in. 

BMW i3

Quirky, interesting, and ultimately excellent around town. That was the general feel about the BMW i3, which impressed with its high-quality interior. It is pricey and takes too long to charge, though…

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Matt Campbell:

“I want one,” I told the guys when we completed testing – it has a beautiful interior, its silly door layout is a talking point, it possesses urban-friendly dynamics and it has teacup piggish looks.

But it’s not exactly the technological masterpiece that BMW set out to create. It takes way too long to charge (a Tesla can get 80 per cent charge in 20 minutes at one of its free Supercharger stations), the range for both the EV and this range extender isn’t as big as it should be – it needs a bigger fuel tank for those emergency trips outside of the urban jungle – and there’s, dare I say it, too much performance.

You can choose Eco Pro or Eco Pro+ modes if you’re really in to getting as much mileage as possible from a charge, but if BMW could find a way to dull the electric motor’s zippy response in the regular Comfort mode as a means of eking out some extra range, it would be a nice pay-off.

Trent Nikolic:

Around town, the i3 makes the most sense in electric terms and if you’re not planning on leaving the urban confines too much, it is entirely easy to live with.

The range claimed by BMW rings true in the real world, too, which means most of us would be able to run around week to week and barely ever dip into the petrol generator range-extender. But it takes a while to recharge via a conventional socket though, and that could be a burden for buyers.

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Curt Dupriez:

It goes like the clappers but, really, I couldn’t drive something so pretentiously styled.

It’s so far beyond harnessing technologies to merely benefit emissions and fuel consumption and so much more about yelling a statement about it from mountaintops.

Behind the wheel, wrapped in its pomposity, it’s as if the BMW is constantly yelling at me.

Marcus Sroba:

The first thing I thought was ‘Wow! This thing is cool’. It looks like a proper sci-fi vehicle. A lot of brands attempt that with their EV and hybrid cars but end up being too silly looking or they get cold feet and end up making them pretty bland. The selection of materials used on the inside is nice, like the wood veneer dash top. I’m not a fan of the gear selector on the stalk near the steering wheel, though.

I was very surprised at how nippy it was. It flung around streets like a pinball. I did find it pretty stiff, though, and think it would be pretty hard to live with around Sydney’s over speed-humped roads.

In the inner-city suburbs, like where I live, the i3 would be great because it’s tiny and easy to park, and I could leave it there for days on end. But then I remembered it’s nearly $70,000 … and there are plenty of other frugal small cars available for that money – or even a third of the price.

Citroen C4 Cactus

Diesel = good grunt, but only if you can use it. The gearbox of the French small SUV caused plenty of consternation among our drivers, but all applauded those funky air-filled bumps on the outside which protect from trolley bumps and car door dings.

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Matt Campbell:

Yet another quirky looker of this quartet, and one that justifies its design with useful elements like those AirBumps on the doors and bumpers. This could be the perfect city runabout for urban-based mums and dads…

Except that the diesel C4 Cactus is one of the most divisive cars we’ve ever had at CarAdvice. The little 1.6-litre four-cylinder turbo diesel engine is refined and willing, but its means of transferring grunt to ground – a six-speed semi-automatic gearbox – is vexing. You can work around the transmission’s tuggy gear changes by lifting off the throttle, but the question remains “should you have to?”. And the answer is a resounding “no”.

In many ways this is a likeable urban driver – light steering, easy to park, responsive to drive. I could live with the gearbox, but based on the day’s feedback, most people couldn’t.

Trent Nikolic:

As the most efficient diesel five-seater on the market, the Cactus makes a lot of sense whether you spend all your time around town, or touring longer distances. But around town there are a few question marks over its drivability.

The diesel works well in traffic, but the auto gearbox isn’t perfect. You get used to it and quickly find the smoothest way to use it, but that really depends on whether you are willing to compromise on your driving style.

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Curt Dupriez:

I discovered that the elements that make the Cactus oh-so-French and interesting – the novelty quilted door skins, that semi-automatic transmission – were those I tired of most quickly; particularly that gearbox around town.

With that transmission, and its around-town grumpiness, the Cactus perhaps makes more sense for country owners.

But I do especially like that the stop-start system, which engages at low speed on the move, doesn’t kill the electric steering assist as it does in so many other cars with the same feature.

Marcus Sroba:

I think the Cactus looks fantastic. Citroen did a great job of integrating the AirBumps into the design. It somehow manages to look urban and rugged at the same time. The interior is a pretty simple affair. The handbrake that looked like a regular automatic gear selector annoyed me but the push button drive select was cool.

I’ve never come across a semi-automatic transmission before, and can understand why they aren’t popular. It became a game of trying to pre-empt the gear changes to get a smoother drive, which was fun for a while but the novelty could wear off very quickly. It would probably deter me from buying a Cactus if it came down to it.

I also wasn’t too impressed by the ride; I know Citroen are renowned for their supple suspension and all, but this didn’t seem like a ‘quality’ ride and it certainly feels the cheapest of the bunch (which it is).

Toyota Prius

Ugly. Ugly. Ugly. Not ugly? Three out of four ain’t bad. This test certainly wasn’t about appearances, but the majority of drivers felt that the Prius doesn’t do enough to move its own game on, despite the fact it is proven and still one of the most frugal cars in the real world for reasonable money.

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Matt Campbell:

I may be the only one here that finds the Prius endearing and still important. The other guys all smacked it down for a bunch of reasons, and while I think it’s one of the ugliest vehicles ever made, it is undeniably a proven force in the world of eco driving.

It is, without question, the biggest car here, and definitely the best Prius yet to drive. But in Toyota’s (or Akio Toyoda’s, more specifically) quest to make the brand’s cars more fun to drive, it has compromised the city-friendly qualities of the Prius to an extent. It thumps over bumps and is noisier than its competitors on this test.

Toyota really should reconsider its silly stance on plug-in hybrids. The Prius Prime, which has even better city-friendly electric range, could easily attract a price premium over the regular model, and eco freaks would love it.

Trent Nikolic:

The Prius is, as usual, a little underwhelming – maybe even more than usual in this company. It works perfectly well around town but there are a few factors working against it. Electric power only doesn’t last long enough to rate a mention and the Prius is only truly efficient around town.

The Prius seems to me to be an example of hybrid tech for hybrid’s sake rather than really adding to the experience.

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Curt Dupriez:

The Prius could get away with supreme quirkiness when its hybrid shtick was fresh and revolutionary, but it now seems weird for weird’s sake. From the feel of the brakes to the drivetrain selector, it’s a step removed from driving and operational normality in so many ways and inevitably to little benefit anywhere,” he said.

The exterior styling. Serious. Just. No. Even the wing mirrors appear out of place because they’re really the only normal thing about its appearance.

It has long been a cumbersome drive, and this fourth-gen is still bloated and tad laborious around town. It’s just a hefty car.

Marcus Sroba:

The Prius is the granddaddy of the bunch – and it honestly kind of seems that way. I must admit it is the best-looking Prius thus far—we might have to get your eyes tested Marcus (ed)—but it’s still far from pretty. Inside, it picks up its game with a funky looking interior. I like the centre console and the gear selector is very cool detail.

On the road my first impression was how sluggish the car was. It is a fair bit larger than the others but it seemed seriously slow. I think this would be a rather frustrating thing to live with day to day.

It just seemed to be a little average in almost every respect when compared to the rest of the models we had on the day.

Conclusion

At the end of our 100km of urban driving there was a variance of less than 3km/h in calculated average speeds between the four cars, and the odometers clearly were not synchronised, as there was also 3km difference between the trip computer measurements despite us staying in convoy the entire way.

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So there’s a clear winner in the urban environment, and it’s the BMW i3 range-extender.

This is a little electric plugger that clearly feels at home in the hubbub of the city, and with a fuel consumption of 0.0 litres over 100km of urban driving, it’s hard to argue with. It had 46km of electric range remaining, according to the car’s on-board computer, with an overall remaining range of 179km – pretty close to the claimed range of 300km total.

If you’re into the electricity side of things, it used 16.7kWh per 100km, which seems reasonable. We just hope that there’s a faster charge system in the works, or you’d want to be able to plug in at work and home to ensure it’s always full.

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The next best was the Audi A3 e-tron, which had a predicted 52 kilometres of electric range when we set off. It managed 49km on EV power alone, and continued to revamp its batteries when the possibility arose along the way.

The result in the end was a displayed fuel consumption of 3.9L/100km, with 2km of electric range remaining, and a total range remaining of 542km.

The Toyota Prius did as expected – it was frugal around town – and it relied upon its batteries a lot more than we’d thought it would. The trip computer showed 4.0L/100km, but with 67 per cent of all driving having been in EV mode.

The Prius had a staggering 827km of combined range remaining, according to the dashboard.

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That was extremely close when compared with the sole diesel model here, the Citroen C4 Cactus. The digital display in that car read 840km distance to empty, and it, somewhat predictably, used the most juice: 5.4L/100km. That’s high in this test, but hugely impressive for a practical and comfortable small SUV.

We suspect the diesel-powered Cactus could well be the star player in our highway test. Stay tuned for that…






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