With petrol prices at their highest ever, and chances of a diesel price hike lurking, should one convert to CNG or LPG fuel kits? If so, what are the pros and cons? Here’s what you always wanted to know.

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Compressed natural gas (CNG)Compressed natural gas (CNG) is a cleaner burning gas – though it does release some Greenhouse gases --  when compared with the mainline fuels such as diesel and petrol.

Natural gas is primarily methane, which comprises carbon and hydrogen. This fuel is safe and generally used at home for heating, lighting and cooking. On the performance front, the CNG is highly compressed, due to which its pressure is around 3600psi. For safety purposes, it is stored in highly pressurised, heavy tanks. That is the reason why an empty CNG tank itself weighs about 68-70 kg. A CNG tank usually has a storage capacity of 8-10 kg.

The present and the futureThe government has been encouraging the use of CNG for vehicle transport and it is already available in most of the major cities across India.  According to a Centre for Science and Environment India study in 2010, 150-200 Indian cities will have CNG filling stations by 2014 and about 58 lakh vehicles in India will be running on CNG by the end of 2020. Today, CNG is already the mandated fuel for public transport buses in New Delhi and Mumbai. All commercial vehicles that are older than eight years have to be converted to CNG, to get an entry ticket into the Bharat Stage IV (BS-IV) cities. These conversions have had a maximum impact on reducing pollution in these cities.

The CNG advantageOne can recover his expenses in about two years with a mere daily commute of 15 km a day. If your travel is more, the recovery is faster. The other advantage of CNG is that your cost per km reduces to Rs2.65 per km from about Rs7.65 per km for petrol. The flip side is the performance of the engine may be compromised somewhat.

Liquefied petroleum gas (LPG)Liquefied petroleum gas (LPG) or ‘Auto Gas’ is one of the most widely used alternative fuels. It is also a green gas, and is the third-most widely used fuel across the globe, after diesel and petrol. LPG is also used for cooking purposes at home.

The biggest advantage of LPG is there isn’t much of a difference in the performance characteristics of the engine when compared with petrol. The other is that its empty tank weighs just about 20 kg, or a third of a CNG tank. The LPG tank is also more compact, leaving room for some luggage space in the boot. In a hatchback, this is a crucial difference.

The LPG advantageThe LPG advantage is that, despite being cheaper, the performance of your engine isn’t as much affected as in a CNG.

Different types of kitsCNG and LPG kits come in three different packages:1. Open loop:  These are cheapest kits on CNG and LPG both. These are simple and mechanical, without any electronics. As the name suggests, it is an open loop. As CNG and LPG are clean gases, it really doesn’t affect pollution in the case of an open loop.2. Closed loop: In a closed loop, the exhaust gases are inspected by the sensors and the volume of intake gas is tweaked accordingly to minimise pollution.3. Sequential injection: Sequential injection is the advanced version kit. The mechanism is exactly similar to the manner in which a normal fuel injection system works and the intakes are controlled by an engine control module or ECM. An ECM is a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle. In short, the difference between a sequential kit and conventional one is same as that of multi-point fuel injection (MPFI) and carburretor, respectively.

Different manufacturers of these kitsKits from various manufacturers are available. Some are Indian, some Italian while we also few from Argentina. The Italians ones are our pick. These are the kits manufacturers we prefer.

VerdictLPG and CNG both help reduce your travel expenses by a great margin, but as you are investing and installing one of these kits, please ensure you get it done from an authorised dealer (for safety purposes). Remember you also have to keep the car for 2-3 years at least to recover the cost. Finally, prefer CNG over LPG as it will be cheaper of the two to run and there are more CNG pumps than LPG ones. Sure, you may compromise zippy performance, but that’s fine if your idea is cost-saving. But for those who still want performance like that of a petrol car, then the LPG kit is what we’d recommend. And those planning to buy a new car, go for a factory-fitted LPG/CNG to avoid warranty issues.