LPG Cars – The Ultimate Guide

With fuel prices seemingly ever on the rise, the average motorist is forced to pay whatever the Government and oil companies deem is the ‘fair’ price, but there’s an alternative, LPG cars.

LPG or liquefied petroleum gas to give it its full name is a by-product of refining crude oil, as well as the processing of natural gas liquids. It used to just be burnt off, but these days it’s often captured and used.

In the UK it’s supplied by Autogas, a subsidiary of Calor.

It’s a low-carbon fuel when compared to either petrol or diesel, it also costs roughly half the price of both fuels.

Current prices are around the 60-67p per litre figure, whereas petrol is £1.25 on average and diesel is £1.29.

It may be extreme to suggest you sell an electric car to move to LPG or avoid EVs altogether to move to one, but they certainly have their merits…

ultimate guide to lpg cars
An uncommon sight here in the UK, but LPG is big in Europe.

But it’s not as easy as just filling up with LPG, your car needs to be converted first. This means the addition of a new fuel tank in the boot and another filling cap.

In this LPG cars ultimate guide we’ll look at the following:

  1. How do LPG cars work?
  2. Is LPG safe?
  3. How much does it cost to convert a car to LPG?
  4. What are the costs of running an LPG car?
  5. How much could you save with an LPG car?
  6. How far can you drive with an LPG car?
  7. Are LPG cars better for the environment?
  8. LPG conversion pros and cons

How do LPG cars work

LPG burns in exactly the same way as petrol does; therefore you can’t convert a diesel car to run on LPG.

A large tank, often 100 litres is fitted in the boot of the car. Piping is then run the length of the vehicle with valves at each end, one at the tank and the other attaching the LPG system to the petrol engine.

Autogas LPG nozzle
LPG also goes by its commercial name, Autogas.

The gas is run through a filter the same as petrol is, and there’s also a pressure regulator to keep the system protected, but due to the gas being in liquid form it’s not stored at high pressure so is perfectly safe.

When you run out of LPG, the car will switch back to petrol automatically.

Is LPG safe?

LPG can ignite just as easily as petrol, but it’s stored in a thick steel tank. If a leak occurs, they’re generally incredibly small and not a danger.

Tests carried out by TNO in Holland have confirmed that LPG tanks are safer than petrol tanks in an accident. In the event of a fire, occupants would have three times longer to escape than in a petrol car.

How much does it cost to convert a car to LPG?

As LPG is fundamentally changing the fuel your car is using it’s a big job, there are many conversion companies across the UK and prices are around £1,200 but dependant on the car.

You should only ever have the work carried out by a UKLPG Approved Autogas Installer, your nearest can be found here.

The conversion takes around three days to complete.

What are the costs of running an LPG car?

As we mentioned earlier, LPG is roughly half the cost of petrol, that’s due to a lower fuel exercise duty. Petrol and diesel are charged at 57.95p per litre, whereas LPG is only 31.61 per/kg.

That translates to an average of just 60-67p per litre compared to £1.25 for petrol. So you’d be saving nearly 50% on your monthly fuel bill by making the switch.

How much could you save with an LPG car?

If you’re having your car converted, you’ll have to factor in that cost to the equation.

Let’s say your car can achieve 35 MPG and that you drive 10,000 miles per year. Per 60-litre fuel tank, you could save £29.70 by using LPG, which would save you around £40 per month, £484 a year.

LPG tank Renault Twingo
Some cars make more sense to convert to LPG than others…

That means it would take 40 months or just over three years to pay back the initial installation cost. Only then will you be reaping the benefits and savings of LPG.

You’ll also have to factor in having the system serviced. It’s recommended this should be carried out every 12 months or 12000 miles.

How far can you drive with an LPG car?

There are different sized tanks on the market, some sit in your spare wheel well, while other larger tanks take up room in your boot.

Spare wheel models are around 44 litres, whereas the boot fitted cylinders can be 60 litres and up.

LPG tanks are only ever filled up to 80% of their capacity though, so an 80-litre tank will hold 64 litres.

All the tanks have different names, one that fits in your spare wheel well is a ‘toroidal’, while a ‘full toroidal’ fits into the space beneath your car where the spare wheel should go.

Autogas LPG Fuel Tank
A full toroidal LPG tank.

‘Ellipsoidal’ is similar to toroidal, but with a more rounded top and bottom, these are often fitted in place of existing fuel tanks on Land Rover vehicles.

You can also get the large, basic cylinder tanks – the cheapest option but you sacrifice boot space.

The bigger the tank, the further you can drive on LPG. You do however get 10-15% less range than using petrol, but this is offset by the lower price you pay at the pump.

35 MPG works out to 8.1 litres per 100 kilometres or 62 miles. With a 64-litre tank, you’ll theoretically be able to drive 434 miles.

Combine that with a full tank of petrol and you could well see 700 miles between fill-ups.

You do still need to have petrol in your tank too, the system works at the optimum temperature so you can’t start and run purely on LPG.

Petrol is also required now and then in the combustion process, using roughly 1/5th of a tank of petrol per full tank of LPG.

Are LPG cars better for the environment?

Yes. When LPG burns it creates up to 80% less NO2 than a diesel and around 5-7 times less than a petrol.

Exhaust Emissions
LPG produces less CO2 and NO2 compared to petrol and diesel.

CO2 is also reduced compared to petrol by roughly 15%.

Cars converted to LPG also benefit from a reduction in road tax as they’re now deemed as an ‘alternative fuel’ vehicle, sadly it’s only a reduction of £10 a year.

LPG conversion pros and cons

Although LPG seems like a great money-saving solution, there are plenty of pros and cons to weigh up.


  • Save roughly 50% on your fuel bill
  • Comparable MPG to petrol
  • No noticeable difference in the way the car drives
  • Greener for the environment


  • Costly to install
  • Takes years to recoup the initial outlay
  • Adds weight to your car
  • Can add an unsightly extra filler cap
  • Not every petrol station has LPG
  • The system needs servicing

LPG not for you?

As you can see, you need to be fairly committed and keep a vehicle long term for the savings to pay off, there are also other ways to be greener when it comes to motoring.

Check out some of our other guides to find out more.