Inputs
Compare petrol with
Filled in for you9% interest on the extra price, 10 years, fuel price rises, upkeep, insurance and resale
Verdict
CNG saves you ₹2.06 lakh over 10 years
CNG's ₹90,000 higher price pays back in 2 years 9 months, counting 9% a year interest on it.
The answer changes at 930 km a month: drive less than that and petrol is cheaper.
If fuel prices rise slower or faster: 2 years 7 months to 2 years 9 months.
This answer uses example car prices and distance. Put in yours to get your own answer.
- Petrol car₹29.38 lakh
- CNG car₹27.32 lakh
- Saving a month now with CNG
- ₹3,557
- Fuel cost per km
- ₹5.66 vs ₹3.68
Fuel saved minus the extra price and its interest.
Saved scenarios
What would flip the answer
Each line changes one input and holds the rest.
- Petrol wins if you drive less than 930 km a monthNow: 1,800 km
Not modelled: weigh these yourself
Show the workingEvery step of the sum, with the numbers above.
Show the chart and scenariosHow the gap changes month by month, and how much the answer moves if prices rise faster or slower.
If prices rise faster or slower
- Fuel prices rise 0% a year2 years 9 months
- Fuel prices rise 3% a year2 years 8 months
- Fuel prices rise 5% a year2 years 7 months
Show every monthThe full month-by-month table, with a CSV download.
How this works
Each car’s monthly fuel cost is distance ÷ mileage × fuel price, plus any extra upkeep. The CNG car’s saving adds up month by month, and it breaks even when that running total covers the extra price of the CNG variant. The stricter test also charges interest on the extra price, at your loan rate or what the money could have earned, compounded monthly. Fuel prices rise each year by the rates you set; by default they stay flat.
Worked example
Petrol at ₹101.86 a litre and CNG at ₹95.75 a kg (Lucknow, September 2026), 18 km/L against 26 km/kg, 1,800 km a month and a ₹90,000 premium at 9% a year:
- Distance you drive a month
- 1,800 km
- Extra price of the CNG car
- ₹90,000
- Interest on the extra price
- 9%
- Fuel cost per km
- ₹5.66 vs ₹3.68
- Saving a month now with CNG
- ₹3,557
- Break-even ignoring interest
- 25.3 months
- Break-even
- 33 months, 59,400 km
- Net gain with CNG, 10 years
- ₹2.06 lakh
Assumptions and sources
| Assumption | Value | Source | As of |
|---|---|---|---|
| Fuel prices, Lucknow | ₹101.86/L, ₹107/kg | Lucknow retail price on 19 Oct 2026: ₹101.86 a litre in Goodreturns, BankBazaar and Business Today (goodreturns.in/petrol-price-in-lucknow.html). Indian Oil publishes city prices only by SMS (RSP 155054 to 92249 92249) and its app. Changes daily at 6 am; check at your pump. Green Gas Limited, the city gas distributor for Lucknow (gglonline.net/cng-price): Rs 107.00/kg w.e.f. 6:00 hrs 03.10.2026. | 2026-10-19 |
| Fuel price rise a year (pessimistic / base / optimistic) | 0% / 3% / 5% | CapitalVerdict default assumption from project spec (fuel/tariff rise); user-editable, not a forecast | 2026-10-19 |
| Interest on the extra price (default) | 9% | Project spec default for interest on the extra car price; user-editable | 2026-10-19 |
| Fuel prices, other cities | Kanpur, Noida, Ghaziabad, Agra, Varanasi, PrayagrajNot verified | oil marketing company / city gas distributor retail price | 2026-10-19 |
Questions
Why are there two break-even figures?
Without interest, break-even is when the fuel saved equals the extra price. With interest, the extra price also grows at your loan rate, because that money was borrowed or could have earned elsewhere. The second figure comes later, and the verdict uses it.
Where do the fuel prices come from?
Choose your city under Assumptions. Verified city prices fill in automatically, with their source and date in the table above. Prices change daily, so check your local pump.
Does it include resale value, insurance or kit servicing?
Resale value and insurance are not included. Add any extra yearly running cost, such as cylinder testing or kit servicing, under Extra upkeep.
What if I drive less than the example?
The saving shrinks with distance. “What would flip the answer” shows the monthly distance below which petrol wins with your numbers.