CNG Kit Guide: Best CNG Options, Installation & Conversion Costs

Author: Abhinand Venugopal•Published on: 1/16/2026•6 Minutes
Overview:CNG kits are quite popular on the Indian market, especially in the budget and fleet category. They offer much lower running costs and cleaner emissions. CNG kits have certain disadvantages too, such as lower performance and higher maintenance costs. Here’s everything to know about third-party CNG kit installation, petrol-CNG conversion costs.
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Key Highlights:


  • Third-party CNG kits require RTO approval, as well as insurance company notification afterwards.
  • Factory-fitted CNG options are always the best, though they cost significantly more.
  • Pure-CNG and Diesel-CNG powertrains are too complicated for passenger vehicles.



CNG or Compressed Natural Gas is cheaper and cleaner (in terms of combustibility) than conventional fossil fuels such as petrol and diesel. Measured in kilograms, CNG fuel is generally more fuel efficient as well at the cost of reduced power output due to lower energy density. The latter drawback is considerably masked by employing ‘petrol + CNG’ powertrains in which petrol power automatically or manually takes over when the engine experiences more load (sudden acceleration, inclines, additional passengers or luggage, etc.).


Petrol + CNG variants are lately becoming common across affordable cars, especially those aimed at fleet operations, wherein per-kilometre running costs are crucial. Aftermarket CNG kits, before installation, must be approved by the local RTO and afterwards, must be notified to the insurance company.


CNG Vs. Petrol - An Overview


CNG-specific power plants can theoretically showcase more performance than a petrol engine. For an equal volume of petrol, CNG has a higher octane rating (120-130 vs. 90-100; more resistant to premature ignition) — allowing for a higher compression ratio, superior thermal efficiency and better resistance to knocking.


However, CNG holds less energy per unit volume compared to petrol. Being a gas, it takes up more space in the entire system (including the intake and combustion chamber), leaving less space for air/oxygen (essential for combustion). Less air translates to less support for combustion and hence, lower power generation. Petrol, being a liquid, can leave more space for air while packing the same or slightly lower amounts of energy.


CNG also burns more slowly, and hence, optimal combustion may not occur at the ideal piston position of a power plant that is inherently a petrol engine. Mechanical work done (force of the piston going downwards) is thus lower. This is the primary reason why the ‘CNG’ mode in petrol + CNG cars feels sluggish. Moreover, manufacturers intentionally undertune such engines for long-term reliability. It is not good to have two fuels with two combustion timings/durations within the same mechanical motion constraints.


CNG Kit - The Basics


A CNG Conversion Kit, as the name suggests, converts an existing petrol vehicle into a petrol + CNG hybrid. The kit comprises:

  • CNG tank (usually steel cylinders and sometimes, composite dual-cylinders).
  • Pressure tubes (route the compressed gas safely to the engine).
  • Pressure gauge (indicates if system pressure stays at optimum levels).
  • Regulator valve (cuts gas flow if system pressure exceeds a certain value).
  • Refill valve (inlet for CNG filling).
  • ECU (controls the entire system, working in sync with normal engine operations).

A diesel + CNG combination will not work because diesel engines work on compression ignition and fuel injectors (in place of spark plugs). CNG combusts best in spark-ignition engines just like petrol. Diesel-CNG mills do exist among heavy commercial vehicles and certain industrial machinery, albeit uncommon. 



Types of CNG Kits


Based on the vehicle type and output requirements, there are two types of CNG kits. The quality of either may differ with the CNG kit manufacturer and pricing.



1. Venturi CNG Kit

  • A conventional system that works best with carburetted vehicles (a rarity now).
  • Cheaper and easier to install (no sophisticated wiring or accessories required).
  • No dedicated ECU required (no need to remap the main ECU as well).
  • Abrupt performance (more maintenance required in the long run).
  • CNG fuel consumption is higher due to minimal system intelligence and control.
  • More emissions (due to unevenly burnt CNG-petrol mixture).
  • Unreliable at high altitudes (areas of low air density).

2. Sequential CNG Kit

  • Works best and only with fuel-injected vehicles (hence, the relevant system in this age).
  • A dedicated ECU (or remap of the vehicle ECU) is required, but with the gain of superior fuel efficiency and performance.
  • Low on harmful emissions.
  • Significantly more expensive.
  • Expert installation required.

Types of Sequential CNG Kits


Closed Loop Sequential CNG Kit

  • The most common and ideal system for BS6 vehicles.
  • CNG fuel flow is controlled based on exhaust readings (particularly oxygen levels) from Lambda/Oxygen sensors, to reduce harmful emissions.
  • CNG is injected at timed yet calculated rates into each cylinder for optimal combustion, just like petrol engines.
  • Better driveability and higher fuel efficiency due to system intelligence.
  • Performance could drop at times to achieve lower fuel consumption and emissions.
  • More expensive.

Open Loop Sequential CNG Kit

  • Simpler due to minimal electronics.
  • CNG is injected at preset levels and timings (hence no active air-fuel mixture correction; manual tuning required periodically).
  • Lower fuel efficiency and emission control in comparison.
  • Performance remains nearly the same as long as the driving environment does not vary drastically.
  • Relatively more affordable and easier to maintain.
  • Ideal for older vehicles (pre-BS6 cars with no Lambda sensor).

CNG Kit Pricing & Related Costs



There are several RTO-approved CNG kits currently on sale in India. Popular brands include Lovato, BRC, MIJO, Tomasetto, etc. Here’s a rough pricing of the various kinds of CNG kits discussed earlier:


  • Venturi CNG Kit: ₹15,000-32,000
  • Open Loop CNG Kit: ₹14,000-19,000
  • Closed Loop CNG Kit: ₹20,000-25,000
  • Third-party Complete Kit: ₹45,000-65,000
  • Factory-fitted CNG Kit: ₹60,000-1,00,000

Related Costs:

  • Registration & RTO Endorsement fees: ₹2,000-5,000 (varies with state).
  • Maintenance: ₹7,000-12,000 annually (based on brand and type; lower for factory-fitted options).
  • Insurance: ₹1,500-2,000.

Why Petrol + CNG Cars & No CNG-Only Choices?


Considering the present demand, the level of supporting infrastructure, automotive packaging considerations (CNG cylinders occupy more space) and general awareness, it is not viable to invest heavily into CNG-only passenger cars. CNG fuel is generally aimed at lowering running costs in the affordable segment, where manufacturers’ profits come from volume sales rather than exclusivity. It is economically viable to retrofit something new to an existing technology rather than developing it ground up for a smaller consumer base. However, CNG-only options exist in the commercial three-wheeler market. Meanwhile, the Bajaj Freedom is the only Petrol + CNG two-wheeler in the country.


Why Manufacturer-Installed CNG Kits Work Best


Manufacturer-equipped CNG kits are theoretically better since they are tested to a certain standard in that specific vehicle. The integration is neater, taking into account the vehicle’s bodystyle, weight distribution, space requirements and more. Overall fit & finish is significantly better as well. For instance, the CNG mode-select button would be well integrated onto the dashboard while other vital information is displayed in the existing instrument console or infotainment screen. They boast of existing vehicle warranty coverage. Maintenance costs are lower as well since they are carried out along with the vehicle’s periodic service.


FAQs


1. Does installing a CNG kit reduce engine life?
If installed correctly and serviced regularly, the engine remains reliable. Improper installation may cause issues in the long run.


2. Is government approval required after installation?
Yes, CNG kits must be endorsed in the RC by the local RTO.


3. How long does CNG kit installation take?
Installation usually takes one to two working days, depending on the authorised CNG fitment centre.


4. Does a CNG kit affect a car's warranty?
In most cases, the manufacturer's warranty on engine components may be compromised after third-party CNG installation.


5. How often does a CNG kit need servicing?
Regular servicing is usually set at 10,000 kilometres or may vary slightly depending on the CNG kit brand.