I want to buy a bifuel car: is CNG or LPG better?

More and more manufacturers are betting on alternative fuels, and now it’s the turn of Liquefied Petroleum Gas, better known as LPG or Autogas, and Compressed Natural Gas, better known as CNG. What advantages do they have? Which is better?

We are going to answer every single one of these questions, because these vehicles, known as bifuel, are capturing a large number of sales in our country.

The main difference between LPG and CNG and fossil fuels, petrol and diesel, is that they are much less polluting and have a lower price than them. In addition, drivers who opt for this type of vehicle will have the ECO environmental label from the DGT. This sticker will allow circulation through certain zones of large cities.

Before going into much more detail, it is important to point out that using these fuels can extend the range of the vehicles, since they carry two tanks: one for gas and one for petrol.

LPG and CNG, what are they?

Of the two types of gas, the most widespread is the one called LPG. It has been on the market for much longer and many manufacturers are already fitting it to their models. As the Spanish Liquefied Gas Association states, LPG is “an efficient and sustainable energy source, with a calorific value much higher than traditional fuels, meaning that a liquefied gas flame produces much more heat than that of other energies. In addition, during its combustion, liquefied gas generates 36% fewer CO2 emissions than coal, 15% fewer than petrol and 10% fewer than diesel. Moreover, unlike other energy sources, it does not generate waste.”

“Likewise, 65% of liquefied gas is created during the extraction of natural gas and the remaining 35% is extracted from oil refining (something its detractors rely on to deny it is ecological). Being what is called a natural secondary product, if it is not used, it is lost.” But what is it? LPG is a mixture of butane and propane, two gases denser than methane, which can easily be liquefied by compression.

One of its advantages? There are already more than 800 petrol stations offering this type of fuel. Its price? It hovers around 0.70 euro cents per litre. By contrast, CNG has only around 100 service stations.

For its part, CNG is becoming known thanks to its inclusion in SEAT models and the Volkswagen group. It is important to highlight that “a vehicle powered by natural gas reduces carbon dioxide (CO2) emissions by around 25% compared with a petrol model, and up to 75% of nitrogen oxide (NOx) emissions compared with a diesel variant, while particulate and sulphur dioxide (SO2) emissions are almost nil.” But what is it? It is a compound called methane that is extracted from wells.

What does the DGT say?

According to the Directorate-General for Traffic itself, “CNG and LPG cars fall within the first category, defined as vehicles that incorporate two tanks for two different fuels and a propulsion unit containing at least two different categories of propulsion energy converters.”

Which is better, LPG or CNG?

At present, LPG seems to be offering better results because it has better infrastructure. This fuel is also fitted by a wide variety of manufacturers, and even drivers themselves can convert their vehicle to LPG at the various authorised workshops that exist throughout the Iberian Peninsula.