Petrol vs Diesel vs CNG vs EV: Which Car Is Actually Cheaper to Own?

Buying a car is only half the expense.

The real question is: How much will your car cost you every month and over the years?

A petrol car may have a lower purchase price, while an EV can cost much less to run. Diesel may offer excellent highway mileage, and CNG can be surprisingly economical for people who drive a lot.

So which one is actually the cheapest?

Instead of guessing, you can compare them using our Petrol vs Diesel vs CNG vs EV Cost Calculator.

Enter your local fuel prices, vehicle mileage, monthly driving distance and, if you want a deeper comparison, the vehicle purchase price and annual maintenance cost. The calculator estimates your running cost per kilometre, monthly energy cost and 5-year total cost of ownership.

⛽🔋 Try the Petrol vs Diesel vs CNG vs EV Calculator

Use the calculator above and change the numbers to match your own car and driving habits.

You can edit:

• Petrol price per litre
• Diesel price per litre
• CNG price per kg
• Electricity price per unit (kWh)
• Petrol vehicle mileage
• Diesel vehicle mileage
• CNG efficiency
• EV efficiency
• Monthly driving distance

For a more detailed comparison, open the Vehicle Price, Maintenance & 5-Year Ownership Cost section and enter the purchase price and annual maintenance cost for each vehicle type.

The calculator then compares all four options and identifies the one with the lowest estimated 5-year ownership cost.

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Why Comparing Only Mileage Can Be Misleading

Many people choose a car simply by looking at its advertised mileage.

For example:

“This car gives 22 km/L, so it must be cheaper than a car giving 18 km/L.”

Not necessarily.

Mileage is only one part of the calculation.

What matters is the relationship between:

Fuel/Energy Price ÷ Vehicle Efficiency = Running Cost per Kilometre

For example, if petrol costs ₹102 per litre and your car delivers 18 km/L:

₹102 ÷ 18 = ₹5.67 per km

If an EV uses 1 unit of electricity to travel 6 km and electricity costs ₹8 per unit:

₹8 ÷ 6 = ₹1.33 per km

That difference can become significant when you drive thousands of kilometres every month.

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What Does the Calculator Actually Compare?

The calculator looks at two different questions.

1. Which option is cheapest to run?

First, it calculates the approximate energy cost per kilometre for:

• Petrol
• Diesel
• CNG
• EV

This helps answer a simple question:

“How much does it cost me to drive 1 km?”

It also estimates your monthly energy expense based on your monthly driving distance.

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2. Which option is cheapest over 5 years?

Running cost isn’t everything.

Imagine two vehicles:

Car A

• Purchase price: ₹9 lakh
• Low running cost

Car B

• Purchase price: ₹14 lakh
• Very low running cost

Car B may save money every month, but it starts with a much higher purchase price.

That’s why our calculator also considers:

Vehicle purchase price + 5 years of energy cost + 5 years of maintenance

This gives you a much more useful comparison of the overall ownership cost.

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Petrol vs Diesel vs CNG vs EV

There isn’t one fuel type that is automatically best for everyone.

Your ideal choice depends on how much you drive, where you drive and how much you pay for energy.

⛽ Petrol

Petrol cars are often attractive because of their relatively simple ownership experience and wide availability.

Petrol can make sense if:

• You drive relatively few kilometres
• Most of your trips are short
• You want a lower initial purchase price
• You don’t want to worry about charging infrastructure

However, higher fuel costs can become noticeable for high-mileage drivers.

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🛢️ Diesel

Diesel vehicles can be attractive to people who cover substantial distances, particularly on highways.

Their strong fuel efficiency can reduce the cost per kilometre.

Diesel may be worth considering if:

• You drive long distances regularly
• Highway driving is a major part of your usage
• The diesel model’s additional purchase cost makes sense for your mileage

But don’t judge diesel purely by its mileage figure. Compare its purchase price, maintenance and actual fuel cost too.

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🟢 CNG

CNG is often considered by drivers who want a lower running cost without moving completely to an electric vehicle.

It can be particularly interesting for people who drive frequently in areas with convenient access to CNG stations.

Consider:

• CNG price in your city
• Real-world CNG mileage
• Availability of filling stations
• Additional purchase cost
• Maintenance requirements

Your actual result can be very different from someone living in another city, which is why the calculator lets you change the CNG price.

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🔋 Electric Vehicle

EVs can have a major advantage in energy cost per kilometre.

But electricity consumption is just as important as the vehicle’s claimed range.

For this calculator, EV efficiency is entered as:

km per unit of electricity (kWh)

For example:

If your EV travels 6 km using 1 kWh and electricity costs ₹8:

₹8 ÷ 6 = ₹1.33 per km

However, real-world EV efficiency can change depending on:

• Speed
• Traffic
• Air-conditioning
• Driving style
• Weather
• Vehicle load
• Battery condition
• Charging losses

For a better estimate, use your vehicle’s real-world efficiency rather than relying only on the manufacturer’s claimed figure.

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Your Monthly Driving Distance Matters More Than You Think

This is one of the most important inputs in the calculator.

Suppose you drive only 500 km per month.

The difference between two fuel types may not be large enough to justify paying several lakh rupees more for a vehicle.

But if you drive 2,000–3,000 km every month, even a small difference in running cost can add up quickly.

For example:

₹3 per km × 2,000 km = ₹6,000 per month

That’s:

₹72,000 per year

And over five years, before considering other factors:

₹3.6 lakh

This is why your annual and lifetime driving distance should be considered before choosing a fuel type.

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Don’t Forget the Purchase Price

A common mistake is to compare only fuel expenses.

Let’s say:

• Petrol car = ₹9 lakh
• EV = ₹14 lakh

If the EV saves ₹4 per kilometre, that’s excellent.

But the EV starts with a ₹5 lakh higher purchase price.

How quickly does the lower running cost recover that extra amount?

That’s the kind of question a total-cost comparison helps you investigate.

The calculator includes the vehicle purchase price so you can see the bigger picture.

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Maintenance Cost Matters Too

Fuel isn’t the only recurring expense.

Different vehicle technologies have different servicing requirements.

For the calculator, you can enter an estimated annual maintenance cost for:

• Petrol
• Diesel
• CNG
• EV

These figures are only estimates, so replace them with realistic numbers for the specific models you’re comparing.

A ₹5,000 difference in annual maintenance may not sound significant, but over five years it becomes:

₹25,000

When combined with fuel or electricity savings, purchase price and other ownership expenses, these differences can change the final ranking.

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How to Get the Most Accurate Result

For a useful comparison, don’t simply leave every value at the default.

Step 1: Enter your local energy prices

Fuel prices vary between cities and can change over time.

Enter your current:

• Petrol price
• Diesel price
• CNG price
• Electricity tariff

Step 2: Enter realistic mileage

Don’t use the highest mileage number you have seen in an advertisement.

Use your real-world average whenever possible.

Step 3: Enter your monthly kilometres

Check your recent driving pattern.

If you normally travel 1,500 km per month, use approximately 1,500 rather than guessing.

Step 4: Add vehicle prices

If you’re deciding between actual models, enter their approximate on-road prices.

Step 5: Add maintenance estimates

Use service costs from the manufacturer or your actual ownership experience where available.

Then let the calculator compare the results.

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A Simple Way to Understand the Result

The calculator gives you several useful numbers.

Cost per km

This tells you how much energy you are approximately spending for every kilometre.

Monthly fuel/energy cost

This estimates what you could spend based on your monthly driving distance.

5-year total cost

This combines:

Purchase price + 5 years of energy cost + 5 years of maintenance

The calculator then highlights the option with the lowest estimated 5-year total.

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The Cheapest to Run Isn’t Always the Cheapest to Own

This is perhaps the most important takeaway.

An EV can have the lowest running cost per kilometre but still have a higher overall 5-year cost if its purchase price is substantially higher.

Likewise, a petrol vehicle can have a higher running cost but still be competitive for someone who drives very little because its initial purchase price may be lower.

That’s why you should look at both numbers:

Running Cost → How expensive is each kilometre?

Total Ownership Cost → How expensive is the entire ownership period?

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Who Should Use This Calculator?

This calculator can be useful if you’re:

• Planning to buy a new car
• Comparing petrol and diesel variants
• Considering switching to CNG
• Thinking about buying an EV
• Comparing different fuel options for a family car
• A high-mileage commuter
• A taxi or fleet operator
• Trying to estimate your long-term car expenses
• Curious about how much your current car really costs to run

You can also use it simply as a what-if calculator.

Change the fuel price or mileage and see how the result changes.

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Try Different Scenarios

One of the best ways to use the calculator is to experiment.

Try your normal monthly driving distance first.

Then increase it.

For example:

Scenario 1: 500 km/month
Scenario 2: 1,500 km/month
Scenario 3: 2,500 km/month

You may find that the best option changes as your annual mileage increases.

You can also test different electricity tariffs, fuel prices and vehicle prices.

This makes the calculator useful not just for today’s decision, but for understanding how your choice could change under different circumstances.

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A Quick Reality Check Before You Buy

Calculator results are estimates—not a guarantee of your actual ownership expenses.

Real costs can vary because of:

• Changing fuel prices
• Electricity tariffs
• Real-world mileage
• Traffic conditions
• Driving style
• Maintenance and repair costs
• Insurance
• Tyres
• Depreciation
• Financing/loan interest
• Charging losses
• Unexpected repairs

The calculator focuses on the major costs included in its inputs. For a complete buying decision, you should also consider factors such as safety, reliability, resale value, practicality and charging/fuelling availability.

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Final Verdict: Which One Is Best?

There is no universal winner.

Low annual driving? A petrol car may remain financially attractive because of its lower initial cost.

High annual driving? Lower running costs can become much more important.

Convenient CNG access? CNG may offer an interesting middle ground.

Home charging + high daily usage? An EV can become particularly compelling.

But don’t rely on general statements like “EV is always cheaper” or “diesel gives the best mileage.”

Put your own numbers into the calculator.

Your driving pattern, local energy prices, vehicle price and maintenance costs determine the answer.

🚗 Calculate Before You Buy

Use the Petrol vs Diesel vs CNG vs EV Cost Calculator above, enter your actual numbers, and compare the estimated cost per kilometre, monthly energy expense and 5-year ownership cost.

A few minutes of calculation today could help you avoid making a very expensive assumption tomorrow.

Change the numbers. Compare the options. Then decide based on your own driving.

Important: Fuel and electricity prices change, and actual vehicle efficiency and maintenance costs vary by model and usage. The calculator provides an estimate for planning and comparison purposes and should not be treated as financial advice.