LPG Fuel Conversion
September 10, 2005 12:12 PM   Subscribe

LPGFilter: No, I don't want to filter out LPG, I am considering getting an LPG conversion for my car...

Here in the UK, LPG is becoming a widely available fuel option. There are several LPG filling stations that I have seen around my area, so I was wondering about getting my Ford Focus (W reg, 1.8 LX, Zetec). These people at greenfuel seem to have some useful information, but I'm wondering if anyone has anybody has had any experience with LPG cars, LPG fuel, LPG conversions, Greenfuel, or anything LPG related. Do you have an LPG success/horror story? Is there anything I should know that they don't tell you?
posted by gaby to Travel & Transportation (15 answers total) 1 user marked this as a favorite
What does LPG stand for? It may go by another name here in the US (like 'petrol' vs. 'gasoline').

Here in the US we have what we call "LNG", liquid natural gas, perhaps thats the same thing.
posted by delmoi at 1:02 PM on September 10, 2005

LPG = propane.
posted by milkrate at 1:28 PM on September 10, 2005

It stands for Liquefied Petroleum Gas. Specific information can be found here.
posted by gaby at 2:01 PM on September 10, 2005

I should say that LPG is about 1/3 the cost of petrol in this country. According to the numbers, it will pay for itself in a couple of years, based on the cost savings between petrol and LPG.
posted by gaby at 2:02 PM on September 10, 2005

LPG = Liquefied Petroleum Gas in the UK and yes, it's Propane. LNG = Liquefied Natural Gas and is what it says, but of that 90% is Methane (therefore much more volatile, involving much greater pressures and lower temperatures).

LPG is old news in places like New Zealand and now very tax efficient in the UK (we have lots of the stuff and don't know what to do with it). Aside from being cheaper it's also greener, as a simpler hydrocarbon it produces fewer and more benign partially consumed byproducts, basically the exhaust is cleaner.

LPG conversion involves fitting a duplicate fuel system to a car, usually a pressurised tank in the spare-wheel bay and duplicate injectors. The car can then run on either petrol or LPG. LPG mileage is slighly inferior to petrol mileage and performance is marginally off, but LPG is half the price per litre. For people doing a lot of driving it makes good sense.

I know Greenfuel personally and I would recommend them highly. They know their stuff, they are completely genuine (their true mission is cleaner air, but as two ex Bath MBA students they're trying to make a business out of making the world a better place). They have recruited some very experienced mechanics and they are extremely fussy about the kits they use. So it's all good really, I assure you that you'd be in good hands.

Downsides with LPG in the past have been the poor quality of some kits and botched conversions - cheap conversions can be just fine but for the unlucky few they can cause severe mechanical problems later on. You may well get some horror stories - particularly from New Zealand which, as I said, was early to the game and suffered at the leading edge. Other issues have been the stop/go messages from the UK Treasury about the long term tax treatment of LPG, which made big companies reluctant to invest in the infrastructure and you'll still find filling stations are few and far between in some places, although I believe this is changing. The UK Government has now given long term assurances so LPG will continue to be much cheaper than unleaded or diesel for some time. Finally in the UK there has been a pretty much disastrous regime of conversion grants which have been mismanaged so comprehensively as to almost strangle the market at birth. I can't remember the exact details but it's a tragi-comedy of government ineptitude.

I think the equation is pretty simple now. If you do a lot of miles a year, upwards of 15,000 then an £2,000 LPG conversion should have a payback within 18 months or so and after that you're in profit. Greenfuel's calculator will show that more clearly. If you get it done properly there should be no reliability issues. The only consideration remaining is the resale value. Opinions differ here. Some say that it has no effect whatsoever, some say it has a small detrimental effect. If it does have a detrimental effect this is based on unfamiliarity with the concept - really what's not to like? As LPG becomes more common and people start to understand what it's about (which they don't right now) this should disappear.

The only thing that they may not be telling you is that you'll probably loose your spare wheel (that's where the tank will go). They'll give you one of those aerosol puncture repair kits - which is not a complete substitute. You'll have to judge for yourself whether that's OK or not.

On a Ford Fiesta, if you have a high annual milage and you can afford the up-front costs there's really no reason not to. Do check that there's a convenient LPG station close to you. There are real environmental benefits too, lower Carbon Dioxide emissions and fewer harmful particulates. Just get it done properly. Best of luck.
posted by grahamwell at 2:09 PM on September 10, 2005

Focus, sorry.
posted by grahamwell at 2:13 PM on September 10, 2005

Just to touch on grahamwell's mention of resale value: here in Australia, LPG vehicles generally have an appreciably lower resale value. Probably because most LPG conversions are taxis or fleet vehicles - high mileage, and most likely poorly cared for (that is, general driver wear and tear; fleet vehicles are generally well-maintained by the fleet operator, but treated like shit by their drivers).

Which all adds up to lower resale - people who particularly want LPG in a used car are rare, and just as likely to spend the money on a retrofit. And everybody else is suspicious that the vehicle has been "tarted up" for sale.

If LPG is just starting to become available/common in the UK, it may pay to keep these things in mind. Environmental advantages go out the window when they meet public perceptions...
posted by Pinback at 8:17 PM on September 10, 2005

2000 pounds!? Here in AU it's about $2500 (1000 pounds) for a conversion. I had one in my commodore (big V8 sedan) which saved me loads and loads of money in fuel. A smaller car like a focus will take longer to pay off, but you should still save in the long term. However, it might be a very long term, depending on the price difference between petrol and LPG where you are.

You can expect fuel efficiency (L/100km) to go down by 10-20% compared to petrol, so figure that into your calculations. Price difference and km/year should tell you the payoff rate, so see how long your fuel savings will take to wipe out the 2000 pounds; it may be many many years, during which time you could have been earning 5% on the capital cost....

So do the numbers carefully. No need to worry about the technology though, it's quite mature now. You don't have to get a spare-wheel tank, I had a big 80L cylindrical tank which took up half my boot and left the spare where it was. Talk to the installers and they'll tell you the options on fitment available to your car. Also ask them about having your engine computer reprogrammed - with a bit of effort, you can increase the power back to what it was on petrol or go for max efficiency; the stock timings (chosen for petrol) will be sub-optimal for LPG. Make sure you get a "dual fuel" installation so that you can switch over and run on petrol.

You may need to get it adjusted every 6-12 months and many mechanics won't know how to do it, so get recommendations from your installer or have them do it.
posted by polyglot at 8:30 PM on September 10, 2005

Pinback: my car-salesman friend used to tell me that LPG made no real difference to resale price, just made the thing a bit easier to sell (might be different in the UK!). All the people I talked to while selling the commodore were very, very interested in the LPG installation. A fleet car is always a harder sell anyway, regardless of LPG.

With petrol going up 50% in the last year and LPG not, I would expect LPG fitment to become more of a bonus. All the conversion places here are now booked out for 3 months in advance.
posted by polyglot at 8:34 PM on September 10, 2005

I've been running propane in the bulk of my vehicles for the last 17 years, my father for over 30. This is very mature technology in Canada.

The numbers about lowered economy are about right with one caveat. If your engine can make use of a higher octane fuel propane is rated at about 105 depending on inpurities. You can make way more power with the right engine than with even the best gasoline. For a while I was running a big block Chrysler with compression bumped to 12:1 with out any detenation and I'm currently building up a caravan with a turbo 2.5l that I expect to be able to run 25-30 psi without worry. I don't know what the legalities in th UK are but anyone with medium mechanical skills can convert a car.

Drop me an email if you've got any questions.
posted by Mitheral at 9:02 PM on September 10, 2005

from gaby's link:
In the past it has been considered waste and flared off.

Please get a bicycle and stop contributing to the insanity. Please!
posted by Chuckles at 10:05 PM on September 10, 2005

You can expect fuel efficiency (L/100km) to go down by 10-20% compared to petrol

polyglot is correct, peak power output will also be reduced. This is because LPG has a higher octane number than petrol. As the engine's ignition timing curve is mapped for petrol the LPG will not burn as efficiently. I've carried out a programmable, dual map, ECU installation and dyno tune on a dual fuel Australian delivered Ford F350 (factory EFI). The total timing difference between standard unleaded and LPG was 12.5 degrees, additionally, the LPG produced 15 horsepower more (at the wheels) compared to petrol.

Ford Australia was selling Falcons with 'factory' (Tickford) LPG dual fuel as an option. I've dynoed these and they produce exactly the same power on either fuel. These vehicles were using a separate timing computer to provide a suitable ignition curve for the LPG.

Another consideration is the type of LPG conversion. Most taxis in Australia use an Impco installation. There are better systems available, (in my opinion only), this is one of them.

The other good thing about LPG is that is doesn't 'wash' the oil from the piston bores and contaminate the engine oil (as all petrol operation does), one of the reasons that taxis on LPG get big mileages from engines before failure/rebuild.
posted by fullysic at 2:09 AM on September 11, 2005

Had LPG for about 4-5 years now. Works great. Haven't had it "adjusted" or anything, it just works perfectly. Another benefit is you don't need to change your oil very much, as it stays as clean as the day you put it in for years.

Only problem with ours is it only takes 45 litres, so that's about 250 miles before a refill.
posted by wackybrit at 5:16 AM on September 11, 2005

fullysic writes "I've dynoed these and they produce exactly the same power on either fuel. These vehicles were using a separate timing computer to provide a suitable ignition curve for the LPG. "

The power can still be there but you'll get lower milage than with gas. A litre of propane contains less energy than a litre of gasoline.
posted by Mitheral at 6:27 AM on September 11, 2005

Mitheral writes: "The power can still be there but you'll get lower mileage than with gas. A litre of propane contains less energy than a litre of gasoline."

No arguments there, the price differential alone in Australia prior to recent world events (approx AUS$1.15/l for petrol and $0.40/l for LPG) makes LPG proportionally more attractive the greater the distance travelled.
posted by fullysic at 2:55 AM on September 12, 2005

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