Making cents of alternative fuel

By DAVID LINKLATER

Petrol and what it costs: one of this year's hottest topics. Hot enough to have New Zealand motorists, traditionally wedded to the concept of petrol power, thinking hard about alternative fuels.

The timing for Ford's new dedicated LPG AUII Falcon couldn't have been better. Amid fears that Kiwis might have to think twice about running big-six sedans - still the country's biggest-selling segment - in the face of spiralling petrol prices, the LPG Falcon seems to offer buyers cake and plenty of scope for eating it too.

The hook is the lower price of LPG. At the time of writing 91 unleaded petrol was 87 per cent more expensive than LPG at the pump - $1.20 per litre compared with 64 cents.

Availability is not a big issue, either. Over 600 petrol stations - about a third of New Zealand's total - now carry LPG.

Case closed? Not quite. Ford's Tickford-designed single-fuel LPG system is offered with the automatic-transmission Forte, Futura and S models, adding $1500 to the purchase price, so there's that to consider.

And a litre of LPG does not fuel a car as far as a litre of petrol, so the pump price seems more attractive than it really is.

How much real-world saving does LPG offer the Falcon owner in Kiwi driving conditions? To find out, Automotive News put two Falcon Futuras - one petrol, one LPG - to the test.

The petrol candidate was the new $44,500 All Black Heritage Series - a limited 300-run extra-equipment model, but with Ford's standard straight-six automatic drivetrain.

Our $45,500 LPG Futura carried the full conversion. On dedicated gas Falcons (a dual-fuel version is also still offered) the petrol hardware is removed, including the tank, fuel lines, pump, injectors and fuel rail.

The LPG tank is mounted neatly underneath the car, although it does cut into the spare wheel well. There's a space-saver mounted in the boot instead, which reduces luggage capacity from 528 to 416 litres.

There's little difference in power outputs between the two cars. In petrol guise Ford's 4.0-litre produces 157kW at 4900rpm and 357Nm at 3000rpm. The LPG equivalent makes 143kW at 4500rpm and 362Nm at 2750rpm.

An identical real-world test route was used for each car, comprising equal portions of stop-start urban running, motorway cruising and winding back roads.

The test route was driven twice in each car. The first was an "easy" run, travelling at the speed limit (and not below unless traffic conditions dictated), but driving with economy in mind: very easy on the throttle and use of the cruise control.

The second "power" run also adhered to the speed limit, but involved heavy application of the throttle, more braking (and thus more acceleration) and was tackled without using the cruise control.

The cars were carefully brimmed at the start and end of each run, using the same petrol and LPG pumps each time. The automatic transmission was run in Economy mode for the easy test and normal for the power run. The air conditioning was switched off.

Over the test route the petrol car posted an impressive 9.75 litres per 100km (29 mpg) on the easy test and 14.65 litres (19 mpg) over the power run.

The LPG car returned 13.47 (21 mpg) and 19.55 litres (14 mpg) respectively.

Bringing the different fuel costs in line, the petrol car cost 11.7 cents per kilometre to fuel over the easy run and 17.6 cents over the power run.

The LPG car cost just 8.6 cents and 12.5 cents, despite using an average of 35 per cent more fuel over the two runs. Overall, the petrol Falcon cost 4.1 cents more to fuel per kilometre than the LPG car.

You could also put the results into perspective by weighing the price of LPG according to the extra consumption. Add 35 per cent on to the cost at the pump and you're paying (in theoretical terms) 86 cents a litre for LPG compared with petrol's $1.20.

The average fuel-cost saving of 4.1 cents per kilometre on LPG means that the $1500 cost of the conversion would be paid for in about 37,000km of mixed motoring at today's prices.

Range could potentially be an issue for the LPG car, but it carries a 92-litre tank - as it happens, exactly 35 per cent larger than the petrol car's. Opt for the LPG wagon and you'll go even further, with a 115-litre tank.

There are many other reasons to choose LPG, of course: it is claimed to emit 10 per cent less carbon dioxide from the tailpipe than a petrol car and 80 per cent less air toxins. Overall, smog-forming emissions are claimed to be reduced by 30 per cent.

But if cutting your fuel bill is the main concern, consider this: our tests show that a lead-footed Futura driver could slash petrol costs to the tune of 50 per cent just by modifying his or her behaviour behind the wheel. No alternative-fuel hardware to fund, no fancy driving techniques, no significant loss in A-to-B travel times.

That's an extreme case, of course. But an overall improvement of, say, 30 per cent should be child's play for the committed driver. That's equivalent to paying 86 cents per litre for your petrol instead of $1.20, which is what you'd save if you maintained your heavy-footed ways but switched to gas.

Opt for LPG and you might have to wait a year to truly start saving; improve your driving and you'll lighten the load on the wallet straight away. Fuel for thought.