2015 Economy Invitational

2015 Economy Invitational

Feature stories about fuel economy are usually pretty boring. Driving frugally while sitting in a steamy cabin bathed in your own sweat as you obstruct the flow of traffic for miles on end is hardly the stuff of legend. So we decided to do things differently. This year motoring.com.au conducted its inaugural Economy Invitation. The idea was to test the five most popularly researched vehicles – not hyper-miling hatches no-one buys – against the Carsales Network to see which adhered most closely to its ADR Combined cycle fuel figure. The results surprised us.

The Cars
People research cars with us. Lots of people. Lots of cars. In short, they want to make the most informed purchasing decision they possibly can. We know all that because we like to keep up with what our readers want, and take notice of their major interests.

If we can add to a buyer's information base, we make every effort to help.

So, the idea was hatched to take a look at our five most researched cars from across the Carsales Network of sites and check their manufacturer's claims around fuel consumption.

We were quite surprised at the variation in vehicle types and categories that were thrown up in regard to heavily researched cars. They certainly didn't fit into a simple particular niche. Indeed, the grouping was quite disparate, although the medium-sized all-wheel drive SUV sector was well represented.

The cars included the locally-built Ford Falcon XR8, Jeep's strong-selling Grand Cherokee, the all-new seven-seat Kia Sorento, segment leading Mazda CX-5 and the evergreen Nissan X-TRAIL. In brief that's two diesels (Jeep and Kia), and three petrols (Falcon, Mazda, Nissan).

Configurations varied as well. There were three four-cylinders (Kia, Mazda, Nissan), a V8 (Falcon) and a solitary V6 (Jeep). Two were naturally aspirated (Mazda, Nissan), one supercharged (Falcon) and two turbocharged (unsurprisingly, the two diesels on test).

Transmissions were all 'autos'. The Falcon, Kia, and Mazda featured a regular six-speed automatic, the Jeep an eight-speed auto and the Nissan a continuously variable transmission (or CVT). All featured all-wheel drive except the rear-wheel-drive Falcon.

Right, you got all that? Good. You'll be tested later.

The Brief
The idea was to put the five cars through a well-planned route, taking in a wide variety of roads. From twisty country backlanes, to the suburban commute and freeway running, we wanted to replicate as many on-road possibilities as we could.

This way, we reckoned we would get as close to a useable and trustworthy figure as possible. A real-world number. We would monitor fuel consumption across our 45km route and weigh the cars against the official data released by manufacturers – along with comparing the figures registered by the cars' individual trip computers.

To add a bit of spice to the event, our three testers were given entirely different briefs on how to drive (see accompanying table for results breakdown for each driver).

Road Tester Adam Davis was instructed to drive as absolutely frugal as possible, coasting whenever the chance existed and making every post a winner when it came to not using fuel. No accessories, no air-con and little to no braking (unless his life depended on it).

Road Test Editor Matt Brogan was assigned to drive 'with an eye to fuel economy'. Not over the top, but employing smooth operation, using Eco modes where available, applying minimal heavy braking and with little to no accessory use.

For myself the brief was easy: Drive as you would normally.

Clearly, they don't know how I normally drive, but for the sake of the test, I did as asked. Just got in and drove. I have to say that it was quite odd to consciously think of how one drives when not consciously appraising it. But, I think I hit the mark.

To end up at our final number, we combined the three drivers' results. And, the results were interesting, to say the least…

The Economy Equation
Even with all the science at hand, argument rages as to what makes for a fuel efficient car.

There are basic tenets of course, such as smaller capacity cars will generally use less fuel than those of larger displacement, lighter weight is better and a slippery shape will stop less air. We know all that.

Less clear are things like CVT transmissions versus conventional automatics.

There can be no doubt CVTs are increasingly used for efficiency reasons. By continually altering the relationship between engine speed and power transmitted to the wheels, a CVT can ensure that no more fuel is used than is absolutely needed at any point.

But CVT-equipped cars use more revs, which can mean more fuel use. And this was an area that came up very regularly on our test. The manner in which a particular configuration is driven, with its unique idiosyncrasies taken into account, has a marked effect on economy.

Further illustrating this was the turbocharged versus naturally aspirated engines question, which is further complicated by diesel versus petrol engines. It's generally understood that naturally aspirated cars need smoother and gentle feed of throttle to aid efficiency. This makes them less efficient in stop/start running.

Of course, countering this is the fact that naturally aspirated engines burn fuel at a slower rate than a wound up turbo. Again, driving technique becomes crucially influential to any economy test.

Myriad other elements affect economy. Tyre pressures and wheel sizes, roof racks and cross bars (a large, blunt roof-top cargo box, for example, can impact fuel economy by as much as 25 per cent at 100km/h.

Then there's length of your trip, the use of accessories… the list is long. We tried to use cars as representative as possible of the most researched models on the website. There was minor add-on and spec-level differences between cars, but not enough to dramatically skew results.

So, we filled them up, returned them to factory settings and ran them around our loop time and again.

The Results
Let's look at each car individually and see how it performed (in alphabetical order).

Ford Falcon XR8
What a grunt factory! The supercharged engine only needs a whisper of throttle to maintain traffic pace. Downside here is that if you use anything more, the fuel use simply skyrockets.

The torque on offer allows sixth gear to be utilised from 72km/h in manual mode with more than enough 'pull' to cope with that gearing.

Unsurprisingly, there's no Eco mode of course, but, unlike the other cars on test, manual shifting appeared to significantly aid economy.

Considering big tyres, old-school hydraulic steering and its weight, the car does surprisingly well. After all, this ain't no Honda Zot.

Claimed fuel economy ADR combined (L/100km): 13.7
As tested fuel economy average(L/100km): 14.7
Discrepancy (L/100km): +1.0

Jeep Grand Cherokee Laredo
There's no escaping the Jeep's weight. It's a bit of a fatty at 2267kg and easily the heaviest car on test. It certainly felt its weight on the uphill section of our course.

There is excellent torque on offer once the turbo is working and helping the car is an eight-speed automatic transmission, offering options to maximise fuel frugality in most situations. The transmission looks to change to a more appropriate gear ratio frequently.

Manual shifting is available, but, curiously the Eco program is deactivated in this situation.

The fat tyres, large wheels and boxy body shape mean the Jeep doesn't coast as well as some others in downhill sections, limiting fuel saving opportunities.

Given the nature of permanent all-wheel-drive and the substantial size of the car, it really is a bit of a marvel of efficiency.

Claimed fuel economy ADR combined (L/100km): 7.5
As tested fuel economy average(L/100km): 7.7
Discrepancy (L/100km): 0.2

Kia Sorento Platinum
The Sorento was the second diesel on test along with the Jeep. The Platinum is the primo model of the range which has it pretty weighed down with electronic goodies. Hence, the quite surprisingly heavy weight of the car, tipping the scales at 2036kg (making it the second-heaviest car on test).

All that weight makes very a good coasting package on downhills, and the car's new upgraded engine offers very good low-end torque. It makes use of its mapping well, with understated, but efficient power on offer.

In fact, considering the Kia has a six-speed transmission and a smaller displacement than the Jeep, it required less revs to do the same job.

The Eco mode is smart, altering transmission shift points, allowing the car's brain to help with fuel economy. We found it best left to the car when trying to maximise efficiency, with manual operation only likely to lessen economy.

Claimed fuel economy ADR combined (L/100km): 7.8
As tested fuel economy average(L/100km): 9.2
Discrepancy (L/100km): +1.4

Mazda CX-5 Maxx Sport
The Mazda calls for a good degree of throttle more to come up to speed with other traffic (for example, freeway merging), but surprisingly the fuel consumption effect is minimal.

The car coasts well on downhill sections and its keener handling allows the driver to maintain momentum into roundabouts and through corners. This of course, has a good effect on fuel efficiency.

There is no Eco mode available with the CX-5, only Normal and Sport. This seems a little odd. With fuel efficiency the word on everyone's lips, Mazda needs to look hard at this [Ed: though we should note it does arrive with an idle-stop system].

Like the Nissan X-TRAIL, although not surprising given the fact that they are both naturally aspirated, the CX-5 needs to make use of its gear ratios to keep things tipping along.

All testers noted that the transmission offered very smooth gearchanges, and enjoyed that it will cleverly will hold a gear when it 'knows' that's required.

It has to be said that the big hill in the course knocked the stuffing out of it', requiring foot to the floor operation . Yes, she's a big hill.

The CX-5 engine is under-stressed at the speed limit, but if you are about maximising fuel consumption, it is best to take your time accelerating to speed.

Claimed fuel economy ADR combined (L/100km): 7.4
As tested fuel economy average(L/100km): 8.0
Discrepancy (L/100km): +0.6

Nissan X-TRAIL ST-L
Under acceleration, the X-TRAIL is pretty uninspiring. There's a lack of torque and this is very noticeable.

The CVT demands pretty high revs, but again, the key to getting the most out of the car's fuel economy is to keep revs as low as possible. This makes for a slow build of steam, but a reasonably efficient fuel useage table.

The large hill purposely built into the route saw the X-TRAIL scrabbling down through ratios, which called again for lots of revs. The car appreciates a very smooth approach, and, let's face it, that's what it's likely to get in the sort of useage for which it is intended. Yes, it's an SUV, but you are not climbing Big Red in this one.

Body roll and soft handling (which besets many candidates in this market segment) make carrying momentum through corners difficult, which in turn, soaks up fuel. Helping good economy are the car's low rolling resistance 'eco' tyres, allowing a degree of ‘coast' and saving fuel as a consequence.

Eco mode and switchable all-wheel drive are both available, and using two-wheel drive ensures minimal drivetrain losses, thus improving economy.

Claimed fuel economy ADR combined (L/100km): 8.3
As tested fuel economy average(L/100km): 9.5
Discrepancy: +1.2

Davis did indeed register the lowest fuel useage. Whether it is feasible in the real world is doubtful, but knock yourself out. Brogan's brief of minimising braking and accessory use, thinking ahead and being conscious of fuel use also registered a much better grouping of average fuel numbers than Leech's 'devil may care' approach. But he could still carry on a conversation and was not totally immersed in a mad economy drive.

In fact, check the accompanying graph (below). Based on the results therein, we reckon it does indeed pay to monitor your driving with an eye to fuel use. Brogan's numbers were substantially better than Leech's but not a whole lot worse than Frugal Davis.

And, he still has people that will get into the car with him as a consequence.

The moral here? Think about your driving, be conscious of how your behind the wheel behaviour affects your economy, and you'll be definitely save a sum worthy of the effort.

The Verdict
Ladies and gentlemen, we have a winner. The Jeep Grand Cherokee Laredo was the car that returned the fuel economy figures closest to those quoted by the manufacturer – a measly 0.2L/100km above the claimed figure.

At a tested 7.7L/100km the Jeep was remarkably frugal as well, taking the most economical car on test gong. Its size belies its fuel economy, and we really has to rub our eyes and look again when the results were tallied.

Second closest to the manufacturer claimed pin was the Mazda with plus 0.6L/100km, followed by the Falcon (plus 1.0L/100km), then the Nissan (plus 1.2L/100km) and finally the Kia (at plus 1.4L/100km).