I am a vehicle LPG conversion specialist.

There are a lot of misconceptions about LPG conversions, it seeems a lot of people don't understand the pros and cons or how to compare vehicle running costs. A lot of people, when given the facts, think LPG seems too good to be true, some of those people go on to generate misinformation or to repeat other people's misinformation. First you need to remember that there is nothing special about any fuel. Petrol needs additives to prevent engines from suffering detonation damage, the frist diesel engine ran on peanut butter oil and most diesel engines (except newer common rail models) still can! LPG doesn't need additives to protect the engine from detonation damage, it is arguably a more suitable vehicle fuel in the first place!

The most important reason anyone converts a vehicle to LPG is to save money on fuel bills. I have just checked average fuel prices in Leeds on 'whatgas'. Petrol is 129.2, diesel is 135.6, LPG is 70p. Actually it is only 65p at 3 garages near me, but I don't need to worry about 5p per litre difference to make this point! Let's do some sums on a small car like the original poster was thinking of buying - I looked at the Citreon C3... Petrol version prices are a bit cheaper (£1000 difference to buy new, much more difference second hand?) than equivalent spec diesel versions, this difference in vehicle price would in itself pay for an LPG conversion and maybe with cash left over (I would convert any petrol C3 to LPG for £1000). Diesel economy is 65mpg, petrol economy is 45mpg. Running on LPG would in the worst case mentioned on this thread use 20% more LPG than petrol so LPG economy would in the worst case be 36mpg. With an anual mileage of 20000 miles per year, the diesel would use 307 gallons (1400L) costing £1898, the petrol would use 444 gallons (2022L) costing £2612, the LPG would use 512 gallons (2333L) costing £1516. These figures are based on the pessimistic figures provided by others on this thread but still show that the LPG driver would be £382 per year better off that the diesel driver, even in the first year!

LPG is available at around 1 in 8 garages, it can also be bought from many gas suppliers like Calor, Flogas, etc, who have filling facilities on their sites (usually even cheaper than at garages). Converted vehicles can still run on petrol at the touch of a button. If the LPG tank runs out, the vehicle will seemlessly switch back to petrol there is no grinding to a halt!

Someone has said it will cost £1500 to convert a small 4 cylinder car, that's false it will cost around £1000. The same person said that £1500, put towards fuel costs, would pay for fuel more or less for the fore-seable fuure. Simple maths should tell him that £1500 privides less that £30 fuel for less than 1 year, and he hasn't considered at all the extra cost of buying the diesel version in the first place. By his own logic, he could save money by buying a cheaper petrol version and putting that saving towards buying petrol...

Has been said that LPG causes engine valves to wear faster. This is true on some makes of vehicle where that make uses particularly soft metal for the engine valves. Such vehicles should be fitted with an engine valve lube system at the same time as the LPG conversion, a valve lube system adds £50 to the cost of an LPG conversion and adds around half a pence per litre of fuel in terms of running costs (the lube fluid is used at the ratio of 1:1000 compared to fuel), hardly a big deal and this works to prevent engine valve wear. But the majority of vehicle makes do not need a valve lube, the Citreon would not need a valve lube. Anyone who thinks engine additives don't work should note that some of Citreons diesel models come factory fitted with an additive system that feeds speical fluid into the exhuast to try to increase the lifetime of the expensive diesel particulate filter - Citreon even build a special additive warning light into the dashboard instrument cluster to tell the driver when the system fluid is running low, messages also flash up on the instrument cluser to tell the driver to drive diesels faster to prevent particulae filter damage!

LPG is a clean burning fuel, better for the environment, better for engines. Engine oil doesn't even change colour for thousands of miles, cleaner engines means longer engine life.

Traditionally, diesel engines were more reliable than petrol, there was far less to go wrong, no electronics, just a reliable mechanical fuel distribition pump. These days it seems diesel engines are less reliable than petrol - modern diesels use just as complex electtonics as petrol engines, but now compared to petrol they have far less reliable and much more expensive fuel injectors, expensive diesel particulate filters that get blogged (especially if you drive them slowly), expensive dual mass flywheels that break (especially if you drive them quickly), exhaust gas reciirculation valves that are more likley to go wrong (in dirty diesel exhausts) than on petrol vehicles.

Simon

I think most people who run LPG cars run on LPG for far far more than 50% of the time. Depends on the length of your journeys and the size of your tank, of course, but even with a small tank you'd expect a 250 mile range, so, so long as you know where LPG is sold, you can always fill back up.

On that subject, no-one's mentioned that filling LPG is usually rather slow: Not had one myself but I hear it can take several minutes. Which can be inconvenient if there are also two people ahead of you in the queue for the pump..

Some good points being made, i'll try to answer some of Robs.

1. No one with any sense will convert a car with a view to selling, it makes no sense, most people with LPG cars try to run them as long as they can, resale is of no interest to most of us.

2. Most converters fit a toroidal tank in the spare wheel well, so this effectively rules out those car with no spare wheel, no one ever said that LPG is for everyone, its a niche market for people who can work round the few shortcomings, and yes boot space is one of them. The tank and equipment are quite light, its the fuel that weighs, but most people only keep a couple of gallons of petrol in the tank so the overall weight penalty is probably in the region of 20lbs.

3. I think 20k miles is about right for most cars for ''payback'', we haven't yet struggled to find LPG, but then we plan trips to include well priced LPG sites, and i wouldn't have entertained the idea in the first place unless there was reliable well priced fuel locally.

Again, this fuel isn't for everyone, people who buy motorised shopping trolleys wouldn't get the benefit, and those of a nervous disposition shouldn't bother either, running on LPG takes a bit of nous and forethought, those who lack those attributes shouldn't bother.

I run on LPG for around 95% of the time, on a trip it could well be 99% or more.

People get the idea that everything must have a value, hence the worry for non LPG users about ''payback'' time, LPG converts don't look at things quite like that, yes there is a cost element or we wouldn't do it, but most LPG users convert proper cars and not shopping trolleys, some of these proper cars can be bought cheaply, will last almost for ever with good care and are actually nice to drive...and far too many modern cars that cannot be said about.

Its also a good fuel for dissidents, if you, like me, are fed up to the back teeth of our governments demanding, taking our money in ever increasing amounts and p ing it up the wall on foreign aid/wars and keeping the feckless, the filling your car for £35 instead of £60 every single time does help soothe the furrowed brow.

Whats really interesting is how anti some people are about LPG, even though they wouldn't consider it themselves for a variety of reasons, they try their damndest, without any personal knowledge of it, to dissuade others from doing so.

Its my fuel of choice for the forseeable, i'm not remotely interested in modern cars, i wouldn't give you a thankyou for a modern Diesel, i do not want the tat that they stuff in modern cars either, i want a 6 pot petrol engine and a proper TC gearbox, and we have two cars that fit that bill, both of them cover about 23 to 25 mpg on petrol, both are LPG converted, the MB is excellent and is virtually as economical on gas, the H6 Outback has only been through one tank of gas and is currently doing just over 20mpg...i have no doubt when it goes into the converter for re-calibration after 1000 miles or so that it will be returing 22/23 mpg.

The bonus with operating cars like this is that depreciation is almost nil and you have Diesel fuelling costs without the stink, the deafening tractor engine and the ticking time bomb bills...now if you want to talk about depreciation, then we'll see some figures that will make the LPG losses look positively puny, 3 years depreciation on a £25k car could buy and convert about 8x6 pot autos.

Each to their own?

Edit...no insurance premium hike and no trouble getting cover from proper quality insurers, fill up time about the same as a normal petrol tank.

Edited by gordonbennet on 24/04/2014 at 19:11

I was told off previously by gb for selling my LPG converted Astra.

Let me explain-I loved it, but it became surplus to requirements and I sold it with a clear conscience for £600 to a fellow who lived close to me, who ran it for another year without problems, and then sold it on to a mate.

It seems that most of the hostile opinions about LPG cars and conversions are being expressed by those who do not actually have any experience of running such cars.

I converted a 10 year old Astra 1.6 8 valve with 62.5k andrn it for 100k without problems commuting up the M5 to Sandwell for the 4 years before I retired.

It was the cheapest car I have ever run,taking into account purchase price,running costs, conversion, and depreciation.

I would suggest asking several converters for advice about suitable cars to convert, give them your possibles,and see what they say,and ask about the need for flash lube, and the extra cost for that.