Petrol and diesel at fuel pump

Petrol vs Diesel: Efficiency and Cost of Running

Choosing between petrol or diesel power is one of the very first decisions you’ll make before purchasing a new or even a pre-owned car. While each has its pros and cons, it’s always good to know how the fuel type you choose will serve your individual needs in the long run. For years, the price of diesel and its fuel efficiency has given buyers reason to opt for it, especially where long distance driving is concerned. However, the debate between petrol and diesel is far more complex than it seems, so if you’re wondering what’s better for you, here’s everything you need, to make an informed choice.


Diesel engines are generally more efficient at burning fuel than their petrol counterparts. Depending on the car as well as the engine used, a diesel engine uses 15-20% less fuel compared to a petrol engine. However, the price of this efficiency is a higher premium compared to the petrol variant of the same car. This is mostly due to the use of heavier materials that are designed to withstand higher compression ratios required for a diesel engine’s combustion process.

On the other hand, petrol cars cost less primarily due to the use of lighter materials. Since the compression ratio in a petrol engine is not as high as that of diesel, lighter materials at lower costs can be used, thereby lowering the cost of petrol cars overall. However, higher petrol prices make these cars slightly more expensive to run.

Cost of Running

Now that you have a basic idea about both types of fuel, here are some key factors to consider with respect to cost of running, before you decide on the fuel type best suited to your needs:

Up-Front Price Difference

Diesel and petrol models of all cars sold in India have a large price gap between them owing to the reasons stated above. Let’s give you a clearer idea with the help of an example – the petrol and diesel variants of the Tata Altroz:

Tata Altroz petrol vs diesel price comparison

As evident, the up-front price difference between the petrol and diesel Tata Altroz cars is as much as Rs 1.61 lakh, in favour of the petrol variant. Similarly, the diesel variants of many other cars command a higher premium over their petrol counterparts.

However, in the used car market, the up-front price difference between petrol and diesel tends to be closer for the same car with similar kilometers driven, even though prices also depend on the condition of the car as an additional factor. Comparing the prices of petrol and diesel variants of used Hyundai Creta SX Plus on Spinny, we can find a price difference of approximately Rs. 40,000. This can be lower or higher depending on the exact car you are looking at, but on average, the price of a diesel used car remains higher than a similar petrol car.

Mileage Game

Mileage, a factor Indians obsess over when it comes to finding the perfect car! Diesel engines tend to outdo petrol ones in this department. If we consider the Tata Altroz itself, the ARAI claimed fuel efficiency of the petrol manual is 19.05 kmpl while for diesel it is 25.11 kmpl. This translates to a difference of about 6.06 kmpl. 

Tata Altroz

Let’s say you use your Tata Altroz to commute around 25km daily with fuel prices being constant. With the Altroz petrol, your cost of running would be Rs 122 per day (based on a petrol price of Rs. 93 per litre), while the running cost with the Altroz diesel would be Rs 82 per day (based on a diesel price of Rs 83). This translates to a monthly expenditure of Rs 3660 for petrol and Rs 2460 for diesel. In essence, the diesel variant will save you Rs 1200 per month and around Rs 14400 in a year.

Service and Maintenance Cost

Service and maintenance cost is another crucial factor to consider before choosing your preferred fuel option. Unlike petrol engines which operate on spark plugs, diesel engines solely rely on compression to ignite the fuel. Because of this, the forces that are generated on the components are very high. This is one of the many reasons why diesel cars undergo excessive wear and tear. Moreover, since the price of components used on a diesel engine is relatively higher, the overall service cost of a diesel engine is generally higher than what is offered on petrol. 

Maintenance cost for a diesel vehicle is about 50% more expensive than that of petrol. To have a better idea about this, let us take the example of the Tata Altroz yet again. The service cost of the petrol and diesel variants of the Tata Altroz for 4 years are detailed below:

Tata Altroz Maintenance Charges




1st Year



2nd Year



3rd Year



4th Year



Total Costs



After 4 years, the total running cost in terms of servicing is Rs 28,289 for the petrol Tata Altroz and Rs 34,079 for its diesel counterpart. The diesel Altroz proves to be Rs 1500 more expensive per year than the petrol variant. Thus, the savings made on fuel more than offsets the additional service costs incurred.

Insurance Premium

Another key aspect to consider is the insurance premium. Speaking as per the trend, diesel cars tend to have higher insurance premiums in later years with marginally higher risk cover in comparison to petrol cars.

  • For cars where the ex-showroom price difference is up to Rs 50,000: Expect cumulative insurance premium to be higher by Rs 10,000 over a span of 7 years.
  • For cars where the ex-showroom price difference is Rs 1.25 lakh to Rs 1.5 lakh: Expect insurance premium to be Rs 20,000 more over a span of 7 years.

The Bottom Line

To summarize the scenario of the petrol vs. diesel debate, taking a practical example would be the best. So let us consider once again the example of the Tata Altroz which is priced at Rs 7,10,362 (on-road Delhi) for the base petrol version, and Rs 8,60,548 (on-road Delhi) for the diesel counterpart. The difference of price paid upfront in favour of petrol comes out to be Rs 1,50,186. 

Now let’s calculate how many years it would take to cover up the additional cost paid upfront if you happen to buy the diesel variant. Considering an average running of 15,000km with a Tata Altroz, you can expect the following running costs for the petrol and diesel variants respectively:

Tata Altroz Cost of Running for 4 Years

Yearly Running



Fuel Efficiency



Fuel Price



Yearly Fuel Costs



Total Fuel Costs



Total Maintenance Costs



Total Costs After 4 Years



To nullify the difference in on-road price (Rs 1.61 lakh) paid upfront, you would have to own the car for 10 years before you cover the additional cost of the diesel car. This is past the limit of legal registration for diesel car ownership in Delhi and will require you to sell the diesel car before you start reaping the benefits. If you don’t live in Delhi, you will start to see lower ownership costs for your diesel car compared to a petrol car. However, the average car ownership period is usually five years, which again places the diesel car at a disadvantage.

If you plan to drive less than 15000km in a year and own the car for less than 5 years, diesel cars are the more expensive option to go with. However, if your driving requirements are more than 15000km in a year and you live in a state that allows diesel car ownership past 10 years, then diesel cars provide better value for money in the long run. Thus, for long distance drivers, diesel engines are the best choice, while for those who love taking out their vehicle every once a while, petrol is definitely the smarter choice.

FAQs about Petrol vs Diesel Car

Q. Which is more efficient petrol or diesel engine?

A. A diesel engine is more efficient as it provides more mileage compared to petrol engines.

Q. Should I buy a diesel car for city driving?

A. For low mileage driving in the city, a diesel car is not recommended. Diesel cars only offer great value if your driving features regular highway driving or more than 15,000 km per month.

Q. What is the advantage of a petrol car?

A. A petrol car is usually much cheaper than the equivalent diesel model. Petrol cars are also more suited for regular city driving with less than 10,000 km driven in a year.

Q. Will diesel cars be banned in India?

A.  At the moment, new diesel cars are not banned from sale in India, especially after the introduction of cleaner BS6 diesel engines. However, it is important to note that diesel cars will only be able to run within Delhi for a maximum of 10 years. After 10 years, the car will need to be registered in another state.

Q. How do I choose between petrol and diesel cars?

A. This depends entirely on your usage. If you regularly drive long distances, then a diesel car will fit your lifestyle and provide savings in fuel. However, if your driving is mostly in the city, then a petrol car will provide more value to you.

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