Dual-fuel . . the choice is a fine one
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The Sherpa we have been testing can run on gas and petrol. Which is the most economic? David WilLox has the answer
OUR long-term-test Sherpa was fitted with a Landi-Hartog lpg dual-fuel conversion, enabling the van to run on gas as well as petrol.
This is an option offered by Freight Rover, though the installation work is carried out by Freight Rover dealers who also hold a Landi-Hartog franchise. The technical side of the installation is fairly straightforward, involving a tank to store the lpg in liquid form, a vaporiser/regulator to vaporise and regulate its pressure and a gas carburettor attachment.
But are the economics of lpg so simple? The dual-fuel capability of the Sherpa meant we could do a realistic assessment of lpg costs compared with petrol costs. Although the comparison was not made under test conditions, at MIRA for instance, the conditions were the same for each fuel and were probably more realistic.
The number of one-ton vans on the motorways these days shows that one can no longer assume that most of these vans are destined for local runnin with a builder or small trade: men. Express parcel operator: couriers, light hauliers ... all us Transits or VWs or Sherpa van to dash up and down th motorways.
So, to reflect this fact, we too the Sherpa up the M1 and M from London to Manchester an back again to make the lpg/pc trol comparison. This necessai Hy involved a few miles in ver light traffic from the motorwa into Manchester and back again
The 400-mile motorway rui was covered in overdrive at steady 100km/hr (62mph) as in dicated on the tachograph in th, unladen Sherpa. Not only wa this felt to be a typical speec there was an added incentive td keep to it — for at an indicated 103km/hr (64mph), a distinc droning from the direction of th,
back axle cut in quite suddenly, making cruising at a higher speed for long distances intolerable.
made the run northwards using lpg, starting off with a full tank of gas and a full tank of petrol. Starting the Sherpa in the morning. I needed to press the small, white spring-loaded switch on the dashboard which temporarily enriches the gas mixture (a combination of propane and butane) — without this the Sherpa would not start.
It was immediately apparent that the engine was much qui eter at tick-over speed when run ning on lpg. So conspicuously absent was the noise that I was tempted to blip the throttle at traffic lights, just to make sure the engine had not died on me.
At higher speeds, other sources of noise play a greater part and there was no discernible dif ference between lpg and petrol. Nor could I detect any difference in performances when using the two fuels.
There is no separate dashboard-mounted gauge in the Sherpa to tell the driver how much lpg is left in the tank but the standard fuel gauge should indicate how much gas is in the tank when that fuel is being used. However, an electrical fault in our van led to the gauge reading zero when the gas switch was on; so it was a case of running on gas until there was none left, and then switching over to petrol. Although this may sound a little hit-or-miss, it happened without undue drama and at 60mph-plus on the N16 I got plenty of warning that the gas was running out.
The engine gradually lost power and then faltered, telling me that it was time to move the switch on the dashboard to the petrol position. It is a three-posi tion rocker switch with a central off-position. Going from petrol to gas, one should pause in the middle off-position for a while; it takes a minute or so for the carburettor float chamber to empty before the engine starts to falter.
But switching from gas to petrol is a straight-through move ment and I found that the Sherpa engine picked up again instantly. At 60mph the drop in road speed was negligible. As soon as petrol was selected the petrol gauge started to register. At the motorway speed of 100 km/hr (62mph), the unladen Sherpa in overdrive with its 1,700cc engine running on petrol achieved 1 0.3 5lit/1 0 0 km (27.3mpg). The petrol cost 40.1p per litre (E1.82 per gallon) which is 4.15p per km (6.7p per mile).
Running in lpg, the consumption was 1 1.5 311t/ 1 0 Okm (24.5mpg), le roughly 10 per cent worse fuel consumption on lpg. But the average price for lpg is currently just 28p per litre (£1 .27 per gallon) which means the costs works out at only 3.23p per km (5.2p per mile).
So the fuel cost saving for lpg over petrol is 0.92p per km (1.5p per mile). To offset against this is the capital cost of the lpg equipment and its installation. For the Landi-Hartog equipment in the Sherpa this is about £325. To recoup this cost via the fuel savings achieved on the motorway run one would have to do approximately 35,000km (21,750 miles).
So in purely financial terms the break-even point for the lpg equipment is commendably early — many vans will clock up more than 21,750 miles in their first year and thereafter it's "profit" at the rate of 1.5p per mile. If the van is kept for 80,000 miles, for instance, that adds up to a most attractive nett saving of £874 at current prices when compared with the same vehicle running solely on petrol.
There are also other aspects to be considered. The Sherpa's petrol tank has a capacity of 50 litres (11 gallons) giving a range of around 483km (300 miles). So, on the London-Manchester-London trip, a refill away from home would have been necessary, probably on the motorway where petrol may be lop a gallon more than usual prices.
The addition of the log installation extends the van's range. Capacity of the log tank is 43 litres (9.5 gallons) but a cut-off valve limits the tank to 80 per cent of its capacity, reducing it to 34 litres (7.6 gallons). This extends the Sherpa's range by a further 300km (186 miles) giving a combined petrol and lpg range of 783 km (486 miles) — enough for the Manchester trip, without stopping to buy expensive petrol away from home. This advantage is obviously worth even more if the van's owner has access to private bunkering supplies of petrol at his base.
A small disadvantage of the lpg equipment is the weight it adds to the vehicle; and it reduced the Sherpa's payload by 100kg (2001b). But this amounts only to an eight per cent reduction and is therefore not some thing that is likely to worry most users.
It can be difficult finding a garage that sells log; I called at a few on the off-chance and the response to my request for gas was invariably: "Eh?" Lpgsupplier Calor issues a handy booklet listing many lpg stockists and the lpg equipment manufacturer should also be able to supply a list. Very few of the motorway service areas have lpg — a distinct disadvantage.
Lpg burns more cleanly than petrol, making it particularly suitable if the van has to be driven inside a warehouse for loading or unloading.
But for the money-conscious (and who is not?), the magic figure is that 21,750 mile break-even point for lpg at present day prices. These last four words are perhaps the key ones — at present day prices. The undoubted attraction of lpg lies in its low price per litre in comparison with petrol. The prices of both fuels is largely dependent on the Chancellor of the Exchequer who could almost wipe out or double the savings at a stroke.