Petrol crossed ₹100 a litre in Delhi back in 2021, and it never went back. If you drive a decent amount each week, that single fact changes the entire math of car ownership. CNG is the fuel most Indian buyers now weigh against petrol, and for good reason: it costs less per km almost everywhere in the country.
This guide breaks down the real numbers, not marketing claims. Use the CNG vs Petrol Cost Calculator below to plug in your own car’s mileage and your city’s fuel prices, then read on for the mileage data, the hidden costs, and the break-even math that most comparisons skips.
Quick Answer
In Delhi, petrol sells at ₹102.12 a litre and CNG at ₹83.09 a kg, as of late July 2026. A petrol hatchback averaging 18 km costs about ₹5.67 per kilometre to run. The CNG version of the same car, averaging 25 km/kg, costs about ₹3.32 per kilometre. That’s a saving near 41 percent on fuel alone, before you factor in real-world driving conditions, which we cover further down.
CNG vs Petrol Cost Calculator
Type in your car’s mileage figures and your local fuel prices below. The tool updates your cost per km, monthly spend, and break-even point as you type.
Fuel Cost Tool
CNG vs Petrol Cost Calculator
Defaults reflect Delhi retail rates as of late July 2026. Prices change by city and by week, so swap in your local petrol and CNG rate before you rely on the result. This tool gives an estimate for planning, not financial advice.
Compare CNG vs Petrol vs Diesel running costs of your Car : Click here
How the Cost Per Kilometre Is Worked Out
The formula behind every fuel cost comparison is simple:
Cost per km = Fuel price ÷ Mileage
For petrol, that means price per litre divided by kilometres per litre. For CNG, it’s price per kg divided by kilometres per kg. Multiply the result by your monthly distance, and you get your real monthly fuel bill for each option. The calculator above does this instantly, but understanding the formula helps you sanity-check the output against your own fuel bills.
CNG Mileage vs Petrol Mileage: The Real Numbers
Manufacturers quote ARAI-certified mileage, tested in controlled lab conditions. Daily driving, with traffic, air conditioning, and stop-start city traffic, brings that number down. Autocar India’s independent road tests give a clearer picture of what owners get on the road:
| Car | Petrol mileage (real-world) | CNG mileage (real-world) |
|---|---|---|
| Maruti Alto K10 S-CNG | 14–16 km/l | 21–24 km/kg |
| Maruti S-Presso S-CNG | 14–17 km/l | 22–24 km/kg |
| Maruti Celerio S-CNG | 17–19 km/l | 26–28 km/kg |
| Maruti WagonR S-CNG | 14–16 km/l | 22–24 km/kg |
| Maruti Swift S-CNG | ~18 km/l† | 27.87 km/kg (Autocar-tested) |
| Maruti Baleno S-CNG | 14–16 km/l | 25–27 km/kg |
| Maruti Dzire S-CNG | 20–22 km/l | 28–30 km/kg |
| Maruti Brezza S-CNG | 13–15 km/l | 22.95 km/kg (Autocar-tested) |
| Maruti Fronx S-CNG | 13–17 km/l | ~19–21 km/kg† |
| Maruti Ertiga S-CNG | 14–18 km/l | 21–24 km/kg |
| Maruti Eeco CNG | ~13–15 km/l† | ~15–17 km/kg† |
| Maruti Grand Vitara CNG | 18–20 km/l | 18–22 km/kg |
| Maruti Victoris CNG | ~18–20 km/l† | 22 km/kg (Autocar-tested) |
| Toyota Glanza CNG | 14–16 km/l | 25–27 km/kg |
| Toyota Taisor CNG | 13–17 km/l | ~19–21 km/kg† |
| Toyota Hyryder CNG | 18–20 km/l | 18–22 km/kg |
| Hyundai Grand i10 Nios CNG | 13–17 km/l | 20–24 km/kg |
| Hyundai Exter Hy-CNG | ~15–17 km/l† | 22.8 km/kg (Autocar-tested) |
| Hyundai Aura CNG | 14–16 km/l† | 20–22 km/kg† |
| Tata Tiago iCNG | 14–18 km/l | ~17 km/kg (CarWale-tested) |
| Tata Tigor iCNG | 14–18 km/l | ~17 km/kg† |
| Tata Altroz iCNG | ~15–17 km/l† | 25.1 km/kg (Autocar-tested) |
| Tata Punch iCNG | ~15 km/l (CarWale-tested) | 20.7 km/kg (Autocar-tested) |
| Tata Nexon iCNG | ~13–15 km/l† | 18.55 km/kg (Autocar-tested) |
| Renault Kwid CNG | 18–21 km/l | not yet officially rated |
| Renault Triber CNG | 17–19 km/l | not yet officially rated |
A Worked Example
Take a Wagon R style hatchback driven 1,500 km a month in Delhi.
Petrol at 16 km/l (realistic city figure) and ₹102.12 a litre costs ₹6.38 per km, or ₹9,570 a month.
CNG at 24 km/kg (realistic city figure) and ₹83.09 a kg costs ₹3.46 per km, or ₹5,190 a month.
The monthly saving lands at ₹4,380, or roughly ₹52,560 a year. That figure lines up with industry estimates, which put real-world CNG savings at 25 to 40 percent of running cost once lab-condition assumptions are corrected for actual traffic and load.
The Costs CNG Buyers Often Miss
A lower cost per kilometre doesn’t tell the full story. Before you switch, account for these:
- Kit or premium cost. A factory-fitted CNG variant typically costs ₹80,000 to ₹95,000 more than the equivalent petrol trim. Aftermarket kits cost less upfront but void parts of your warranty and carry safety risk if not fitted by an authorised dealer.
- Boot space. The CNG cylinder sits in the boot on most hatchbacks and sedans, cutting usable luggage space by roughly half.
- Power drop. Engines tuned for CNG lose around 5 to 8 percent peak power compared to the petrol tune, most noticeable on inclines and highway overtakes.
- Mandatory hydrotesting. The CNG cylinder needs testing every three years under PESO safety rules. Skipping this is illegal and voids your insurance in case of an accident.
- Service intervals. CNG engines run hotter and need slightly more frequent servicing of the fuel system.
None of this cancels the savings. The real gain sits a bit lower than the headline “40 percent cheaper” claim you see in ads.
How much CNG required for 100 km? : Click here
Break-Even: When a CNG Kit Pays for Itself
If you’re buying a CNG variant or fitting a kit, the question that matters is how long it takes to earn back that upfront cost. The formula:
Break-even distance (km) = Kit cost ÷ Saving per km
Break-even time (months) = Kit cost ÷ Monthly saving
Using the worked example above, a ₹90,000 premium against a saving of ₹2.92 per km breaks even at roughly 30,800 km, or about 20 months of driving 1,500 km a month. Drive less, and that timeline stretches out fast. Drive more, such as a cab or delivery vehicle covering 3,000 km a month, and the same kit pays for itself in under a year.
CNG or Petrol: Which Fits You
- Under 500 km a month: The fuel saving stays small in rupee terms, and a CNG premium takes years to recover at this pace. Petrol keeps things simple.
- 500 to 1,500 km a month: CNG usually makes sense if you plan to keep the car for three or more years and have a filling station nearby.
- Over 1,500 km a month, or commercial use: CNG almost always wins. Fleet operators, cab drivers, and long-distance commuters see the fastest payback.
- Limited CNG stations in your area: Even with strong savings on paper, queues and detours to refill eat into the time and convenience you save on fuel cost. India has crossed 6,000 CNG stations with coverage across 600-plus cities, but density still favours Delhi NCR, Mumbai, and Gujarat over smaller towns.
Frequently Asked Questions
Is CNG cheaper than petrol in 2026?
Yes, in every major Indian city, CNG costs less per kilometre than petrol. The gap in Delhi runs close to 40 percent before accounting for kit cost and lost boot space.
How much CNG kit cost do I recover per year?
It depends on how much you drive. A typical private car doing 1,200 to 1,500 km a month recovers a ₹90,000 kit in roughly 18 to 24 months.
Does CNG damage the engine?
A factory-fitted CNG engine, tuned specifically for the fuel, holds up well with regular maintenance. Poorly fitted aftermarket kits carry more risk to engine components over time.
Why is my real CNG mileage lower than the ARAI figure?
ARAI tests run under fixed lab conditions with no traffic, no AC load, and a set driving cycle. Real roads, real weather, and real traffic bring the number down, typically by 15 to 30 percent.