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I was considering buying an old Volvo V70, and came across some comments about LPG conversions. It all sounds very appealing, although I'm no mechanic. From what I've picked up, cars running on LPG get around 80% of the mpg that they get when running with petrol. Eg a 30mpg petrol car would get around 25mpg with LPG. I'm not sure what the current price of LPG is, but it's suggested it's around half that of petrol, so you'd effectively get 50mpg with the above example.
What are the downsides to it, other than the initial cost of installation?
What's the typical cost to convert a car?
Can all cars run on LPG - what about a small economical car which might already be returning 50+mpg with petrol?
I suspect the LPG conversion industry might be home to a few cowboys - is there anything to be aware of?
Doesn't the tank take up a lot of boot space?
deejayenWhat are the downsides to it, other than the initial cost of installation?
More mechanical complexity, for one. Can flumox most independant mechanics if they have to diagnose any fueling or engine issues. Additional ECUs can mean more difficult to find gremlins in the system.
If your wife (or someone who likes simplicity) drives it then switching between lpg and petrol may be an annoying distraction for them. Most systems can be automated and will switch over relatively smoothly when up to temp but it's better to do it manually as this can become problematic if you're doing a lot of stop start driving. Also, you've got two tanks to fill/think about and you need to know where all your lpg garages are.
what's the typical cost to convert a car?
£800 - £1500 ish. Some parts such as the tank aren't a problem to buy second hand.
Can all cars run on LPG - what about a small economical car which might already be returning 50+mpg with petrol?
Yes, just less compelling an argument for the conversion.
I suspect the LPG conversion industry might be home to a few cowboys - is there anything to be aware of?
There are registered and certified installers, you'll need to notify your insurance company so you'll need paperwork to backup the installation.
jon1973 - MemberDoesn't the tank take up a lot of boot space?
Generally doughnut tanks in the spare wheel well.
LPG could be/ should be great but there's limited investment and the technology is really at the level of a refined bodge.
the cost of lpg rises more then the cost of petrol yearly it used to be less than half the price of petrol meaning you would get double the mpg not the case now s.
It's about 55p a litre near me from morrison's, with unleaded about 103/4.
It still appeals to me (given my car's appalling economy), but I'm put off by the 1500 quid conversion cost and the general arse of it all.
Takes alot of trouble free lpg miles to recapture the cost.
Its alot of money to invest in an already old car.
Run an old diesel on veg oil. Still cheaper - not nearly as much as it used to be but cheaper.
It's cheap because there's little/no duty on it. There's little/no duty on it because it's very clean burning (low NOx, almost no SOx), with duty moving towards penalizing a new bogy-man (CO2) I'd expect that isn't going to be the case indefinitely.
Having said that, I thought that 5 years ago when I bought a petrol car, and would have recouped the cost several times over since then!
What are the downsides to it, other than the initial cost of installation?
The additional complexity. A typical modern system will intercept the pulses sent to the petrol fuel injectors and and instead pulse LPG into the inlet in its place. So the original petrol system is the one doing the bulk of the work to figure out how much fuel, and then based on that the LPG system replaces petrol with the correct amount of LPG. Knowing how much LPG is needed is by tuning the LPG system after installation.
However, this method relies on the petrol fuelling system to be in good order in the first place. Cause if the petrol system is injecting the wrong amount, the LPG system could in turn inject the wrong amount.
So yes, they are more complex. You essentially have 2 fuel systems where previously you only had one. It can make the engine bay a little crowded for space in some places.
What's the typical cost to convert a car?
Depends on engine size, and complexity of engine. Typical 4 cylinder I would expect in todays money to be anything between £1 - 2k. A good number of years ago, my V8 4.4 litre cost about £2.5k
Can all cars run on LPG
If you mean completely on LPG, t would be wrong to say blanket Yes. Generally, if its fuel injected, and the injection is into the inlet manifold before the cylinder, then LPG can be done. Some newer engines have the petrol injectors going directly into the cylinder itself. These engines are harder to do because the injectors will rely on petrol going through them to keep them cool. With no petrol, the would burn out. So they would need something like a 25% petrol 75% LPG setup . . . .imagine the complexity in tuning that.
Then you also have valve seat issues. LPG can burn at a higher temp and has little lubricating properties to it. Some engines have valves and valve seats which greatly rely on such lubrication, and so on LPG alone, there is the possibility of the valves becoming damaged.
For example, the Range Rover 4.4 BMW derived engine has valves which can handle LPG fine. The later 4.4 jag derived engine does not, so another valve lubrication system has to be fitted alongside the LPG.
what about a small economical car which might already be returning 50+mpg with petrol?
You really need to sit and do the maths to figure out whether you would get any return. You have to save the cost of converting the car before you really start saving. For example. I reckoned at about 18mpg of my range rover, it would save about £1000 in fuel every 10,000 miles. So it would take me 25000 miles to break even on the cost of fitting the LPG to the car. (i.e. about 2 years for my average mileage)
I imagine at 50mpg then that saving could take a lot more miles to make, and then factor yearly mileage, and you could find it would take years to break even when you could have just spent the money on the petrol in the first place.
I suspect the LPG conversion industry might be home to a few cowboys - is there anything to be aware of?
Even accredited ones can do really rubbish jobs. I've had 2 systems fitted in the past by different people and also fitted a system to an old off roader I used to have. Of the fitted ones, One was brilliant, then other less so. ( my DIY was brill of course ! )
Overall, LPG I reckon has plateau'ed. If you have a car,( or buy one) with it fitted AND you live close to a filling station, then its likely worth it. Other than that, I think that for anything that does over 30mpg, or you have to travel for LPG to fill up, then its just not really worth the hassle.
I've just changed my big 4x4 recently, and bought a petrol V8 4.2litre effort. LPG on the engine would cost probably close to £3k, would need the extra valve lubrication stuff. There is no LPG near me, and frankly LPG would just be a pain in the hoop now. My mileage has dropped over the last year, so would take a lot longer to return on investment.
My Honda FRV runs on it, has just passed 150k miles and was converted at 10k. Runs without any problems. Costs just under 10p mile for a 6seater 2l petrol car. I think it's great. As Diesel starts to fall out of favour I can see it becoming popular once more. Some of the new prins kits are pretty advanced too.
I've had three LPG powered Subarus. One I converted myself and the other two I bought already converted. I only had any trouble with the Outback, which had been used to travel to and from Poland. The valve clearances were done and all was reet again. Other than that, no problems!
I wouldn't pay to have a car converted; it'll be a while before you break even, and you can pick up converted cars for less than an equivalent unconverted one. People are suspicious!
The main point is where is your local LPG seller? It quickly becomes a faff to detour a few miles just to fill up on gas, and you will be doing it a lot! My largest tank was 55litres, so 44l useable, which was good for about 180 miles.
I was lucky; there was an LPG Esso station just around the corner from my daughter's school, but during holidays I had to make a special trip...
And there's more; if the pump breaks, as they sometimes do due to cack handedness, or empties, it's not top priority to fix or fill it. Sometimes it was a week to fill it or a month to fix.
The price of LPG, when petrol prices were dropping like a stone, didn't keep pace, almost wiping out the benefit.
Then you have extra service costs, the lack of a spare wheel, and driving around with a bomb in the boot...
I wouldn't do it again!
suburbanreubendriving around with a bomb in the boot...
Pretty sure that aspect of it is as safe or more safe than an equivalent tank of petrol.
Pretty sure that aspect of it is as safe or more safe than an equivalent tank of petrol.
Possibly, but it's behind the rear axle so makes you think every time you get an Audi up yer chuff.
Pretty sure that aspect of it is as safe or more safe than an equivalent tank of petrol.
It's worse. But this isn't Hollywood, car's don't explode in real crashes.
Petrol sits in a relatively week tank until something ruptures is and then forms a pool which then gives a vapor cloud with the potential to explode, and then a pool fire.
LPG will sit in the tank, which is often inside the car and better protected, which is great until the car's in fire, then it gets hooter, and the pressure rises, until it explodes as a BLEVE and takes out everyone within a hundred meters.
Consequences are far worse, but less likely.
I had a 3.9l v8 Range Rover with lpg. Under slung tanks, as big as you could get but no loss of boot space or spare wheel.
Slightly smoother sounding engine and ever so slightly less power which you only noticed if you manually switched over from petrol to gas or vice versa.
Only 2 stations within a 20 mile radius selling it meant I had to fill up whenever passing or it cost me more just to go and get it.
The systems are the sort of prove whereby it would take years to recoup the cost.
I found when buying/selling the RR that the fact it had a certificated, all singing computer controlled system didn't affect the price but made it more desirable, so I bought over a different vehicle & sold pretty quickly.
(The car came with receipts for the system, over 2.5k. I paid 2k for the whole vehicle & sold it for similar.)
and the pressure rises, until it explodes as a BLEVE and takes out everyone within a hundred meters.
Not with car LPG tanks which have a pressure relief valve. So its more likely to build up with heat, then vent out the valve, causing a flame, but not explosion.
Very good example of it here:
Pretty sure that aspect of it is as safe or more safe than an equivalent tank of petrol.
If that's the case, why can't you take them on the Channel Tunnel?
Thanks for all the great info.
I'll drive past the local LPG stations and see what the price is. I came across a site called FillLPG.co.uk and that shows one (expensive) petrol station near me selling LPG at 80p per litre, which is a lot more expensive than I thought it would be. In contrast, I see that other areas of the UK have it on sale for less than 50p per litre.
A quick calculation of costs:
20,000 miles at 30mpg (petrol) at £1.05 per litre = £3178
20,000 miles at 24mpg (LPG) at 80p per litre = £3026
gives £152 saving over 20,000 miles. No doubt there'd be additional costs with LPG, and you'd probably still end up burning a fair amount of petrol in cold weather etc.
After that, it doesn't seem so appealing...
After that, it doesn't seem so appealing...
Certainly not at present. We're in an odd situation currently regarding the price of petrol. Next year it "could" be £1.50 per litre, lpg at 69-79p starts would be a much more attractive proposition. FWIW I noticed zero difference in consumption between petrol and lpg, if anything I found the car used less gas than petrol. This does vomit in the face of accepted logic so your results may vary.
I'd have one again but probably on the basis that it was in a second car I intended to keep pretty much indefinitely but still wanted to enjoy occasionally. Maybe if I owned some kind of yank tank, V8 pickup or some kind of turbo nutter.
It's also worth remembering that the the car will run on petrol until it warms up and then will switch to LPG in order that it doesnt freeze the injectors. It does this seamlessly, but if you're only doing lots of short journeys, you may not reap the benefits of the system. I do around 30 miles per day, for me it wasn't worth it. 500 miles per month, a 3rd of which would be on petrol anyway meant that it'd take around 6 years to recoup the costs.
Had a berlingo that never ran well on LPG. Could be that the berlingo was rubbish but it drove fine on petrol.
LPG guy said petrol engine had to be perfect, any rough running would be wildly exaggerated. I wouldn't get one again after the hassle.....
Been running a big old Lexus for over three years on LPG. No issues really - it starts and drives like any other car, and if you are running low on LPG you can always switch back to petrol - only had to do this a couple of times in 100,000 miles. Never had an issue finding an LP station in the UK either.
I would happily have one again. Not sure if you would recoup the installation costs on a smaller car, but for a 4.3litre monster it is definitely worth it. I pay under 50p a litre at the moment, but it does vary much more from station to station than petrol does.
If it's a V70 your are set on, forget the petrol version and go for the five cylinder diesel D5. My last couple of drives up the A9 returned 54mpg. You've got to love average speed cameras.
My car is LPG converted and I do around 20k per year.
80-85% of petrol MPG is about right. My LPG costs are typically 11.1p per mile @ around 20 to the gallon, and I pay between 45 and 65p per litre. Driving the same way, I'd be getting 24 to the gallon on petrol, or about 19.9p per mile.
So I'm saving 8.8p a mile, or around £35 a week. I was doing around 31 to the gallon before I had the car converted, which would have been a saving of around £20 a week.
As a comparison with diesel, I drove a delivery mileage 320d which did around 32 to the gallon. Or 15.2p a mile.
So overall, I'm happy that it's saving me cash. And the purchase price of a big engined petrol + LPG is less than a diesel.
The upsides are:
1) Petrol levels of refinement.
2) Cheap running costs.
3) No foul stuff coming out the back of your car.
4) None of the massive diesel specific bills - £1200 injectors, DPFs clogging etc.
The downsides are:
1) Range. I fill up 2-3 times a week, and you need to know where to fill up. My local pump advertises 54.9p a litre, but they have a loyalty scheme that means they average out at 49.9p a litre.
2) You lose some power on a vapour system.
3) Complexity - most LPG systems use the heat from your coolant to vaporise the gas, and intercept injector signals from the petrol ECU. This means joints in plumbing and wiring.
4) Your spare wheel well has a tank in it. The tanks aren't light.
All in, I'd have another LPG converted car, but I'd go for the biggest tank I could fit.
My '87 Uno had the best ever LPG conversion, just a hose going into the air intake and a little screw to regulate the mix. The 900cc engine actually ran better on LPG than petrol. Modern cars are a different story though it seems
Oh, and I understand diesels are a lot more efficient on light throttle before everyone starts saying they get 60mpg in a 320d 😆
The key thing is buying your LPG at the right price - because the headline figure is a lot less than petrol, it's easy to see it all as cheap and pay silly prices. There's a 60% difference between me buying LPG at just short of 50p a litre and the bloke above paying 80p a litre. That's the % equivalent of paying £1.68 a litre for petrol vs £1.05!
If you can't get cheap LPG conveniently, it suddenly stops making so much sense.
Yes, in the above example, I think it would work out at around £1200 saving over 20,000 miles if LPG was 50p a litre, which would probably pay for the cost of the conversion. At 80p a litre it's just not worth it when petrol isn't that much more expensive.
Only really makes sense to buy a car with it already fitted, with a certificate from a reputable place and running well. None of the install costs and all of the very slight benefits.