On the last stage of the three-day Hyundai eco-run around the North Island, there were no doubts our little 1.5-litre Getz turbo diesel would complete the 1059-kilometre distance without refuelling.
At the run-end top-up with the fuel warning light not even flickering, the car took 41.7 litres, which theoretically meant 3.3 litres were still remaining.
But, as economy wizard Hans Tholstrup said, the Getz could easily have taken more than the stated 45-litre tank capacity. Tank capacities often exceed manufacturers’ figures.
Not only did the Getz emit the least carbon dioxide emissions at 118 grams/km, it also averaged the most frugal 3.94 litres/100km (71.7mpg) for the journey.
With an official combined fuel figure of 4.5 litres/100km, the Getz should have been the most economical of the 12 Hyundai models that set out to prove a point.
European figures for the Getz diesel are 5.5 litres/100km for the urban cycle and 3.9 litres/100km for the highway test.
These laboratory tests confirm that it’s not always easy to emulate published fuel consumption figures on the road.
In addition to the Getz diesel, two Sonatas and an Accent diesel also completed the drive without a refuel.
Drivers had the challenge to beat the stated fuel figures by the largest percentage, which meant the largest and thirstiest of the Korean cars could win.
Our 12.4 percent improvement paled again the 30.6 percent registered by the 1.6-litre petrol-engined Accent of David and Trish Kilburn. It went from a published figure of 6.7 litres/100km to a remarkable 4.65 litres/100km.
The problem lay in determining the actual published figures because the government’s fuel figures are an incomplete mess.
Most seem to be sourced from Australian ADR tests, but models like the Getz diesel, Sonata diesel or 1.6 petrol Accent and diesel Accent aren’t sold in Australia and fuel figures were gleaned from elsewhere. So the figures weren’t like for like.
Still, the Hyundai exercise was more than simply improving on published fuel tests. It was all about raising the profile of biofuels that will be available from New Zealand pumps from next year.
Shell provided the 10 percent blend of ethanol (E10) for the petrol cars in the run and biodiesel (B5) for the diesels, with all the cars running a higher blend than the initial government level
Those percentages are higher than the initial government targets but rest assured, ethanol as a petrol blend and biodiesel alternatives to fossil fuel will become a fact of life.
Although they produce lower CO2 emissions, biofuels are slightly inferior to regular petrol and diesel when it comes to consumption, although the industry is reluctant to put a figure on the difference, for fear of public negativity.
So perhaps we would have achieved even better fuel figures had the Hyundais been running on normal petrol and diesel.
David Robinson, the biofuels manager for Shell New Zealand, says biodiesel should be closer to the energy value of normal diesel than ethanol is to petrol. Ethanol is between two percent and four percent less efficient than petrol.
CO2 emissions aren’t a health damaging gas but are the main cause of climate change and arguably the single biggest pollution threat that mankind faces.
Diesels produce less CO2 but more air quality pollutant emissions than petrol, so it’s all a bit of a juggling act when you’re deciding how best to save the world.
The run underscored the good fuel consumption available if drivers set their minds to the task, and was never better proven than by the efforts of Tholstrup.
His 2.2-litre turbo diesel Sante Fe with a five-speed sequential auto gearbox incurred the added penalty of a trailer laden with an Accent – a huge handicap on the long hills on the Desert Road or the steep climb up Mount Messenger on the drive from New Plymouth to Auckland.
Based on an eco figure of between 13 and 14 litres/100km, given the towing imposition, Tholstrup hoped to better this figure, and he achieved a respectable 11 litres/100km.
As the Danish enthusiast pointed out, that’s better than a Ford Territory – without the two-tonne load he endured.
Tholstrup, 61, lives in Queensland and is something of a world sustainability expert.
He created the world’s first solar car 26 years ago and was the first to drive from Brisbane to Melbourne on a 40-litre tank.
He offers some interesting alternatives on fuel economy, and still adheres to coasting, even though modern fuel injection systems shut down on a trailing throttle.
Though he agrees braking is the main enemy of fuel economy (since you need to burn more fuel to regain lost momentum), he stresses brakes are cheaper than engines for slowing down a vehicle.
Most competitors in the eco-run pumped tyre pressures above recommendations. In the case of the Getz, which has a relatively soft suspension, the ride was hardly compromised and the car handled better.
Higher pressures, of course, result in less rolling resistance and better economy, although not all cars take kindly to over-inflated tyres.
Hook a laptop computer up to a car and much can be read into operating efficiencies, such as throttle settings, fuel quality, engine loading, air intake temperatures and engine load. Operate a cigarette lighter in your car and more fuel is used.
By the end of the first day in Taupo, after 314km, the fuel gauge on our Getz had still not budged from full, but we all know how misleading gauges can be.
Day two south on a windy Desert Road via Bulls to Wanganui and north to New Plymouth was the longest haul at 389km, and was dogged by heavy rain.
Still, the fact that our fuel gauge was indicating half full for the start of the final 314km run back to Auckland indicated any refuelling was unnecessary.
At $24,990, the manual only CRDi is the most expensive Getz – you can have a 1.4-litre petrol model for $5000 less – but the willing 1493cc common rail diesel with its variable geometry turbo is a cracker.
Peak torque of 215Nm between 1900 and 2500 revs proved a boon on the eco-run, as the car pulled up steep hills with commendable ease. The Getz even breasted Mount Messenger (the steepest climb on the journey) in third gear.
A trip computer detailing fuel consumption would have been handy but is only available on the higher grade petrol versions.
Some of the drivers who had never tried economy driving were intrigued to find they actually enjoyed the challenge of moderate pace motoring, rather than it being a bore.
So maybe there’s hope for the planet yet.
Or maybe not.
How the other cars fared
The Accent diesel, powered by the same diesel engine as the Getz, averaged a good 4.07 litres/100km.
At the other end of the scale, a flagship 3.8-litre V6-engined petrol Grandeur returned 8.0 litres/100km against an eco figure of 10.8 litres/100km.
The 2.4-litre, four-cylinder, petrol Sonata did 6.79 litres/100km, a good result that was not far short of the 6.1 litres/100km for the 2.0-litre diesel Sonata. Both had four stage automatic transmissions.
The 2.7 V6 petrol Sante Fe auto consumed 9.4 litres/100km, compared to 7.9 litres/100km for a Tucson auto with the same engine.