Thinking about switching your car from petrol to CNG? For many Indian car owners, CNG can be an attractive fuel option because it may reduce the cost of everyday driving and provide an alternative to petrol. However, converting a petrol car to CNG is not simply a matter of installing a cylinder and connecting a few pipes.
A proper CNG conversion involves the right retrofit kit, a suitable cylinder, compatible components, qualified installation, correct calibration, safety checks and the required documentation. Your vehicle also needs regular maintenance after conversion.
Before spending money on a CNG kit, it is important to understand how CNG conversion works, whether your car is suitable, what components are installed, what documents you should receive and how to estimate your potential savings.
In this guide, we explain the important things you should know before switching your car to CNG.
What Does Switching to CNG Mean?
When people talk about switching a car to CNG, they generally mean one of two things.
Factory-Fitted CNG Car
A factory-fitted CNG vehicle is designed and approved by the vehicle manufacturer with the CNG system integrated into the vehicle. The manufacturer takes responsibility for the design, components, calibration and installation as part of the vehicle’s approved configuration.
For a new-car buyer, a factory-fitted CNG vehicle can be a convenient option because the CNG system is designed specifically for that vehicle.
Retrofitting a CNG Kit to an Existing Car
In a retrofit conversion, a suitable CNG system is installed on an existing petrol vehicle. The vehicle must be compatible with an approved retrofit system, and the installation should be carried out by an authorized or appropriately qualified installer following the applicable requirements.
In India, retrofitment of CNG systems is subject to applicable motor-vehicle regulations and type-approval requirements. The Automotive Research Association of India (ARAI) explains that retrofitment of in-use petrol and diesel vehicles is permissible subject to the applicable requirements under the Central Motor Vehicles Rules.
Therefore, you should never choose a CNG kit only because it is cheap or because it has been installed in another vehicle of a similar size.
Should You Convert Your Car to CNG?
CNG conversion can make sense for some vehicle owners, but it is not automatically the best choice for every car or every driver.
Before converting your car, consider the following factors:
- How many kilometres do you drive every month?
- Is CNG easily available on your regular routes?
- Is an approved CNG retrofit system available for your vehicle?
- Can you find a reliable and qualified CNG installer nearby?
- How long do you plan to keep the vehicle?
- Are you prepared to follow the required maintenance schedule?
- Can you afford the complete conversion cost, including cylinder, installation and documentation?
- Does the conversion make financial sense after considering your actual fuel consumption?
If you drive only a few kilometres every month, the financial payback from conversion may take much longer. On the other hand, a high-mileage user may recover the conversion cost more quickly if the difference between petrol and CNG running costs is significant.
Check Your Car’s Compatibility Before Buying a CNG Kit
One of the most important steps is checking whether your particular vehicle is suitable for CNG retrofitment.
Do not assume that every petrol car can use the same CNG kit. Different engines and vehicle configurations can require different components, calibration and installation arrangements.
Before purchasing a kit, check:
- Vehicle make and model
- Manufacturing year
- Engine type and capacity
- Fuel-injection system
- Existing vehicle configuration
- Availability of an approved retrofit application for the vehicle
- Compatible CNG kit and components
- Compatible cylinder and mounting arrangement
- Availability of an authorized or qualified installer
- Availability of after-sales service
A professional installer should check the vehicle rather than simply installing a generic kit because it is physically possible to fit one.
Choose an Approved CNG Retrofit Kit
The CNG kit is one of the most important parts of the conversion. A proper retrofit system is designed and tested for applicable vehicle and engine requirements.
ARAI’s retrofitment guidance states that a CNG kit manufacturer should seek approval from a notified Rule 126 testing agency, with approval involving applicable component, engine and vehicle tests and other requirements.
When selecting a CNG kit, ask the installer for information about:
- Kit manufacturer and model
- Applicable vehicle compatibility
- Type-approval information
- Installer authorization or credentials
- Warranty terms
- Availability of replacement components
- Service and calibration support
- Documentation supplied after installation
A very low-priced kit may not be a good deal if installation quality, documentation, calibration or after-sales support is poor.
What Components Are Installed During CNG Conversion?
A CNG conversion is a complete fuel-system installation. The exact components can vary according to the vehicle and approved system, but a typical retrofit installation can include several major components.
CNG Cylinder
The cylinder stores CNG at high pressure. It must be an appropriate approved cylinder installed according to applicable requirements and securely mounted in the vehicle.
Cylinder Valve and Safety Components
The cylinder is connected to valves and safety components that control and protect the high-pressure CNG system.
High-Pressure CNG Lines
High-pressure lines carry CNG from the cylinder toward the pressure-reduction and fuel-delivery system. Their routing, connections and protection are important for safe operation.
Pressure Regulator or Reducer
The regulator reduces the pressure of CNG from the storage system to a pressure suitable for the engine’s fuel-delivery system.
CNG Injectors
In an electronically controlled system, CNG injectors deliver the required amount of gas to the engine.
Electronic Control System
The electronic control system manages CNG fuel delivery and works with the vehicle’s engine management system according to the design of the retrofit system.
Filling Valve
The filling valve is used to connect the vehicle to the CNG dispensing nozzle at a CNG station.
Switch and Indicators
A cabin-mounted switch or control unit may allow the driver to monitor or select the available fuel mode, depending on the vehicle and system.
Because the CNG system operates under high pressure, installation should not be treated as a DIY modification.
What About the CNG Cylinder?
The CNG cylinder deserves special attention because it is a high-pressure storage component.
Before accepting a converted vehicle, check that the cylinder is appropriate for the application, correctly identified, securely mounted and accompanied by the required documentation.
You should also know the cylinder’s testing requirements and due date. CNG should not be refilled into a cylinder that does not have the required valid testing status.
Never allow anyone to weld, drill, cut, modify or otherwise alter a CNG cylinder. If the cylinder or its mounting appears damaged, the vehicle should be inspected by an appropriate qualified professional.
For more information, see our complete guide to CNG Cylinders and our guide to CNG Hydro Testing.
CNG Conversion Cost: Don’t Look Only at the Kit Price
There is no single CNG conversion price that applies to every car. The total cost can vary considerably depending on the vehicle, CNG kit, cylinder, installation requirements, installer, documentation and local charges.
Your complete budget may include:
- CNG retrofit kit
- CNG cylinder
- Installation and labour
- Additional vehicle-specific components
- Calibration and testing
- Documentation or applicable administrative charges
- Registration-related requirements, where applicable
- Insurance-related changes, where applicable
- Future maintenance and replacement components
Instead of asking only, “How much is the CNG kit?”, ask the installer for a complete written quotation covering the entire conversion.
This makes it easier to compare two installers and avoid unexpected costs later.
Will a CNG Car Give Better Mileage?
Many people expect a CNG-converted car to deliver a specific mileage figure, but there is no universal mileage number that applies to every vehicle.
Actual CNG mileage can depend on:
- Vehicle model and engine
- Condition of the engine
- Quality of the CNG kit
- Installation and calibration
- Driving style
- Traffic conditions
- Road conditions
- Vehicle load
- Use of air conditioning
- Tyre pressure
- Maintenance condition
- Quality of the fuel system components
Therefore, avoid advertisements promising a guaranteed mileage figure without considering your actual vehicle and driving conditions.
How Can You Calculate Your CNG Savings?
The best way to decide whether conversion makes financial sense is to calculate your actual running cost rather than relying on general claims.
You can compare the cost per kilometre of petrol and CNG.
Petrol Cost Per Kilometre
Petrol cost per km = Petrol price per litre ÷ Petrol mileage in km/litre
CNG Cost Per Kilometre
CNG cost per km = CNG price per kg ÷ CNG mileage in km/kg
Estimated Savings
Savings per km = Petrol cost per km − CNG cost per km
You can then estimate your monthly savings:
Monthly savings = Savings per km × Monthly kilometres driven
Finally, you can estimate the approximate payback period:
Payback period = Total conversion cost ÷ Estimated monthly savings
Remember that this is only an estimate. Actual savings will change with fuel prices, mileage, traffic, maintenance and driving habits.
Use our CNG Savings Calculator to make the calculation easier.
Factory-Fitted CNG vs Retrofitted CNG
| Feature | Factory-Fitted CNG | Retrofitted CNG |
|---|---|---|
| Installation | Installed as part of the vehicle’s manufacturer-approved configuration | Installed after the vehicle has already been manufactured |
| Vehicle design | Designed around the manufacturer’s CNG configuration | Depends on the approved retrofit system and vehicle compatibility |
| Kit selection | Specified by the vehicle manufacturer | Must be suitable and approved for the particular application |
| Installation quality | Controlled through the manufacturer’s production process | Depends heavily on the installer and installation process |
| Documentation | Provided as part of the vehicle documentation | Additional retrofit and regulatory documentation may be required |
| Buying situation | Usually selected when purchasing a CNG vehicle | Useful for owners who want to convert an existing eligible vehicle |
What Documents Should You Get After CNG Conversion?
Do not leave the installation centre without understanding the documentation associated with the conversion.
Depending on the vehicle, kit and applicable state requirements, you may need documents such as:
- CNG kit installation documentation
- Kit approval or type-approval information
- Cylinder documentation and test certificate
- Installation invoice
- Installer or retrofitment authorization details
- Warranty documentation
- Applicable inspection or testing records
- Documents required for vehicle registration endorsement
- Documents required for insurance updates
Keep these documents safely. They may be useful during future servicing, cylinder testing, insurance changes, registration-related work or when selling the vehicle.
Don’t Forget Insurance and Registration
Changing the fuel configuration of your vehicle can affect its registration and insurance records.
After a retrofit conversion, check the applicable requirements of your state transport authority and your insurer. Registration endorsement procedures can vary by jurisdiction.
For example, state transport authorities may require specific documents for endorsement of a CNG or LPG kit. The exact process should therefore be confirmed with your local transport authority rather than relying on information from another state.
Also inform your insurance provider about the applicable fuel-system modification and keep the relevant documents.
How Safe Is a CNG-Converted Car?
A properly designed, approved and professionally installed CNG system can be used safely when it is maintained according to applicable requirements.
However, CNG should never be treated as a system that requires no maintenance.
Important safety practices include:
- Use an appropriate approved CNG kit.
- Use a suitable cylinder with valid testing status.
- Have the system installed by an authorized or appropriately qualified installer.
- Inspect the system periodically for leaks or damage.
- Do not modify or weld the cylinder.
- Do not ignore the smell of gas or unusual sounds.
- Do not attempt high-pressure CNG repairs yourself.
- Follow the vehicle and kit manufacturer’s maintenance instructions.
- Do not refill a cylinder when its required testing validity has expired.
- Follow CNG station safety instructions during refuelling.
If you notice a suspected CNG leak, unusual hissing sound or another serious problem, move away from ignition sources and have the vehicle inspected by an appropriate professional.
For more safety information, read our CNG Car Owner Do’s and Don’ts guide.
What Maintenance Does a CNG Car Need?
Switching to CNG does not mean that regular vehicle maintenance can be ignored.
A CNG vehicle still has an engine, cooling system, battery, brakes, tyres, suspension and other vehicle components that require routine maintenance.
Engine Oil
Use the correct engine oil and replace it according to the vehicle manufacturer’s recommended schedule.
Spark Plugs and Ignition System
Because the engine operates on gaseous fuel, the ignition system should be maintained properly. Spark plugs and related components should be inspected and replaced according to the vehicle or system manufacturer’s recommendations.
Air Filter
A dirty air filter can affect engine operation and fuel efficiency. Check and replace it according to the recommended maintenance schedule and driving conditions.
Cooling System
Check coolant level and condition and make sure the cooling system is maintained properly.
CNG System Components
The regulator, injectors, lines, valves, sensors, connections and other CNG components should be inspected by an appropriate service professional according to the system’s maintenance requirements.
Cylinder and Mounting
The cylinder and its mounting should be inspected for damage, corrosion, loose fittings or other problems. Required cylinder testing must also be completed within the applicable validity period.
For practical maintenance advice, see our guide on How to Take Care of Your CNG Car at Home.
What Happens When the CNG Runs Out?
Many CNG vehicles are designed as dual-fuel vehicles and retain petrol as another fuel option. However, the exact behaviour when CNG becomes unavailable depends on the vehicle and the installed system.
Do not assume that every converted vehicle will behave in exactly the same way.
Keep enough petrol in the vehicle to follow the manufacturer’s recommendations and avoid depending entirely on one fuel source, particularly when travelling outside areas with good CNG availability.
Advantages of Switching to CNG
Depending on your vehicle and driving pattern, switching to CNG can offer several potential benefits.
- Potentially lower fuel cost per kilometre compared with petrol
- Useful for drivers who cover high monthly distances
- Availability of dual-fuel operation in many systems
- An alternative fuel option for suitable petrol vehicles
- Potentially lower running expenses when fuel-price differences and actual mileage support the economics
- Useful for commercial vehicle operators who travel significant distances
The actual benefit depends on your local CNG and petrol prices, vehicle mileage, driving conditions and conversion cost.
Disadvantages and Things to Consider
CNG conversion also has some limitations that should be considered before making a decision.
- Initial conversion cost
- Additional weight from the CNG cylinder and components
- Space occupied by the cylinder, depending on vehicle design
- Need for appropriate installation and calibration
- Regular inspection and maintenance requirements
- Limited CNG availability on some routes
- Possible changes in driving characteristics depending on the vehicle and system
- Additional documentation and registration requirements for retrofitment
- Need to maintain the high-pressure fuel system properly
Who Should Consider Switching to CNG?
CNG conversion may be worth considering if you:
- Drive a large number of kilometres every month.
- Own a petrol vehicle that is compatible with an approved retrofit system.
- Have convenient access to CNG stations.
- Plan to keep the vehicle for several years.
- Can find a reliable installation and service provider.
- Have calculated the expected savings instead of relying on assumptions.
- Are prepared to maintain the vehicle and CNG system properly.
Who Should Think Twice Before Converting?
CNG conversion may require more consideration if:
- You drive very few kilometres each month.
- CNG stations are difficult to access in your area.
- Your vehicle does not have a suitable approved retrofit application.
- You are planning to sell the vehicle very soon.
- You are considering an unverified or extremely low-cost kit.
- You do not have access to reliable CNG service facilities.
- You are unwilling to maintain the cylinder and CNG components properly.
10 Questions to Ask Before Installing a CNG Kit
- Is my exact vehicle model and engine compatible with this CNG system?
- Is the retrofit kit approved for the applicable vehicle application?
- Who manufactures the kit?
- Is the installer authorized or appropriately qualified for this installation?
- What cylinder will be installed?
- What documentation will I receive after installation?
- What is included in the quoted price?
- What warranty is provided?
- Where can I get the system serviced in the future?
- What are the applicable registration, insurance and testing requirements?
CNG Conversion Checklist
Use this checklist before paying for a CNG conversion:
- ✔ Check vehicle compatibility.
- ✔ Verify the CNG retrofit system and applicable approval information.
- ✔ Choose a reliable installer.
- ✔ Confirm the cylinder details and testing requirements.
- ✔ Ask for a complete written quotation.
- ✔ Understand the warranty.
- ✔ Confirm what documents will be supplied.
- ✔ Check the applicable registration endorsement process.
- ✔ Inform your insurance provider as required.
- ✔ Keep all invoices and certificates safely.
- ✔ Follow the recommended maintenance schedule.
- ✔ Never modify or repair high-pressure components yourself.
Frequently Asked Questions About Switching to CNG
Can every petrol car be converted to CNG?
No. CNG retrofitment should be carried out only where the vehicle and retrofit system are compatible and the applicable approval and regulatory requirements are met. Do not assume that every petrol car can use the same CNG kit.
Is factory-fitted CNG better than aftermarket CNG?
Factory-fitted CNG vehicles have the advantage of being designed and integrated by the vehicle manufacturer. A retrofit CNG system can also be an option for an eligible existing vehicle when the appropriate system is used and professionally installed.
Is CNG cheaper than petrol?
CNG can have a lower running cost per kilometre than petrol in many situations, but the actual saving depends on local fuel prices and your vehicle’s real-world mileage. You should calculate your own cost per kilometre before making a decision.
Will my car’s performance change after CNG conversion?
The driving characteristics can change depending on the vehicle, engine, CNG system and calibration. The result also depends on the quality of installation and the condition of the engine.
Do I still need petrol after converting my car to CNG?
Many dual-fuel vehicles retain petrol operation, but the exact fuel-switching behaviour depends on the vehicle and CNG system. Follow the manufacturer’s instructions for your specific vehicle.
Is a CNG-converted car safe?
A properly installed and maintained CNG system can be used safely. Safety depends on suitable components, proper installation, valid cylinder testing, regular inspections and following the applicable safety requirements.
How much does it cost to convert a car to CNG?
There is no single price for every vehicle. The total cost depends on the vehicle, retrofit kit, cylinder, installation, components, documentation and local requirements. Always obtain a complete written quotation before proceeding.
Does a CNG car require regular maintenance?
Yes. A CNG vehicle still requires normal engine and vehicle maintenance as well as inspection of the CNG system. The cylinder, valves, lines, regulator, injectors and other components should be maintained according to applicable requirements and manufacturer recommendations.
Can I install a CNG kit myself?
CNG systems involve high-pressure fuel storage and should not be installed as a DIY project. Use an appropriate professional or authorized installation facility for the applicable system.
What should I do if I smell CNG from my car?
Treat an unusual gas smell as a potential leak. Avoid flames and other ignition sources, move to a safe location when possible and have the vehicle inspected by an appropriate professional. Do not attempt to repair a high-pressure CNG leak yourself.
Related CNG Guides
If you are planning to switch to CNG, these guides can help you understand the complete process:
- What Is CNG? A Complete Guide to CNG for Automobiles
- CNG Kits: Types, Components and Important Information
- CNG Cylinders: Safety, Testing and Important Information
- CNG Components and Their Functions
- CNG Fitment Center Guide
- CNG Hydro Testing Guide
- CNG Kit Service and Maintenance
- CNG Service Center Guide
- CNG Car Owner Do’s and Don’ts
- How to Take Care of Your CNG Car at Home
- CNG Savings Calculator
Final Thoughts
Switching your car to CNG can be a practical decision for the right vehicle and driver, particularly when the vehicle covers a significant distance and CNG is easily available along regular routes.
However, the decision should not be based only on the price of the CNG kit or claims about mileage. Vehicle compatibility, approved components, cylinder safety, installation quality, documentation, maintenance and long-term fuel savings are all important.
Before converting your car, calculate your actual petrol and CNG running costs, choose a suitable retrofit system, use a reliable installer and understand the documentation and regulatory requirements applicable to your vehicle.
Most importantly, remember that a CNG system is a high-pressure fuel system. Proper installation, regular inspection and responsible maintenance are essential for safe and reliable operation.
If you are still deciding whether CNG is right for your vehicle, start by learning what CNG is and how it works, then compare your expected running costs using our CNG Savings Calculator.
1 thought on “Switching to CNG? Here’s What You Need to Know Before Converting Your Car”