Is running a car on LPG the cheaper option?

"Something to Gas about"

The price of fuel in the UK seems to be getting ever higher, so how can I reduce my fuel bills?

With fuel tax on the constant rise UK drivers face the highest fuel bills around. Prices quoted in this article are based on UK fuel pump prices and were correct at the time of writing (June 2010) but will obviously change over time.

So what does the beleagured motorist do to save money on fuel prices?

The most obvious way is switching to Diesel, Diesel is around 50% more efficient than petrol, with very little difference in price, maybe a penny or two a litre more. Diesel cars are common and many new ones come in under 120 Grams of CO2 reducing you vehicle excise duty to only £35 per year, or even free if it manages 99 grams of CO2 or less.

But is there an even cheaper way? What about LPG? Liquid Propane Gas works in a similar way to petrol, yet offers two real advantages, firstly it is a lot cheaper being only about 52% of the cost of petrol, and secondly it is a lot cleaner than petrol, thus reducing your CO2 emissions for the green minded ones among TorqueCars members and readers. 

So how would LPG compare in running cost to a diesel, well to work this out we need a test car or two. Let’s take a small car the Fiat 500 and a larger car a Ford Mondeo. First the Fiat. 

So how many miles do you have to do to save money by converting to LPG.

The fiat 500 1.2 base model starts at £8,300 for the petrol or £9,700 for the diesel. Once you have taken into account the cost of the LPG conversion, I received a quote for £1500 for the Fiat, although they can be cheaper ranging from around £1,200+, that brings the price of both cars to within £100 the LPG car costing a little more. 

Below is a brief summary of the running costs.  


Purchase price


Miles per Year

Cost of fuel per ltr

Annual Fuel Cost







500 Diesel






LPG is around 5% less efficient than petrol so I have reduced the cars MPG from 55.4 to 52.5 to reflect this. Even bearing this in mind though the LPG car would give an annual saving of £334 in fuel, obviously the more miles you do the more this would add up. 

What about the Ford? 


Purchase price


Miles per year

Cost of fuel per ltr

Annual Fuel Cost

Mondeo 1.6

Edge with LPG






Mondeo 1.8TDCI






With the Ford you would save £522 per annum doing 15,000 miles per year. The bigger the car, the more you will save in fuel costs because the more fuel it will drink,  

A couple of other factors to bear in mind is the warranty of the car. I asked the Fiat dealer if converting the 500 to LPG would affect the warranty, he answered yes. Even if the wing mirror was faulty and was not related to the LPG conversion it would not be covered once the car had been converted. Of course if you buy a car over three years old and convert it the warranty would have expired anyway.  

Join us in the forum to discuss your experiences with LPG engine conversions with our friendly worldwide members.

Does converting to LPG affect insurance? I did a quick quote on a major comparison website for a 40 year old male with 5 years no claims, with the conversion £230 without £195. Some insurance companies won’t accept cars with any modifications, and so it does limit who you can use. Vauxhall built a “Duelfuel” car, and Volvo a “Bifuel” car so these do not count as modified. But all things taken into account, even converted running costs would be cheaper.  

Check out the car classifieds and search for LPG cars, there are many for sale and they don’t seem to be more expensive than their petrol counterparts so buying one already converted could save you the conversion cost. 

With 1,400 LPG fuel stations around the nation you should always be able to top up, failing that you can always simply switch back to petrol as all cars keep their original tank and system, some have an internal switch to change from LPG to petrol and vice versa, others are automatic. Should you go the LPG route? The choice is yours but should be dependant on your annual mileage, your MPG and how long you intend to keep the car.

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