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 captured and put into use.

    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.

    Any suggestion of switching from electric cars to LPG engines is sure to raise eyebrows. We’re trying to get to petrol-free by 2035, after all! LPGs certainly have their merits. Read on to learn more about this alternative fuel.

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

    You can’t just fill a petrol engine car with LPG. First, you need to convert the car. This means adding a new fuel tank to 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 is fitted in the boot of the car, usually 100 litres in volume. 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 (like petrol is) and there’s also a pressure regulator to keep the system protected. 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 automatically switch back to the petrol from the main tank.

    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 the Netherlands have found 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?

    It’s a big job to switch your car’s fuel source to LPG. There are plenty of providers who will carry out the conversion across the UK, though. Their prices can start around £1,000, although the figure depends hugely on the car and the ease of conversion.

    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?

    Prices last checked August 2022

    Although prices fluctuate, LPG tends to sit around half the price of petrol, per unit. This is due to a lower fuel excise duty. LPG is charged at £0.29 per kilo, whereas unleaded petrol is charged at £0.53 per litre. [Figures accurate for 2022-2023]

    You could save up to half of your monthly fuel bill by making the switch.

    How much could you save with an LPG car?

    Prices last checked August 2022

    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 approx. £56 by using LPG, which would save you around £75 per month, £652 a year.

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

    That means it would take just 16 months to pay back the initial installation cost, at the current prices. 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 12,000 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 capacity, 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.

    The spare wheel models, fitting in the well, are also known as ‘toroidal’ tanks. Whereas, ‘full toroidal’ tanks actually sit beneath the ccar, in the space where the spare wheel would go.

    Autogas LPG Fuel Tank
    A full toroidal LPG tank.

    ‘Ellipsoidal’ is similar to toroidal, but with a more rounded top and bottom.

    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 time 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

    Ready to sell your car?

    Ready to learn more about valuing, maintaining, and selling your car? Check out more of our guides here, covering everything from hybrid and electric car depreciation, to converting your car to dual-LPG fuel.