Now that diesel prices have been increased by Rs. 5 and branded premium diesel by Rs. 19, is it still worth your while to buy a diesel car? Or do you have better options in CNG, LPG or maybe even petrol considering the difference in the purchase cost of the car?

CarToq puts these four fuel choices in perspective and checks if diesel is still the most attractive fuel as it’s made out to be – as this year the demand for diesel vehicles far outweighs that of CNG, LPG or petrol. Companies that have car models in both petrol and diesel engine choices see nearly 80% of the demand for the diesel variant – this applies to premium hatchbacks mainly such as the Maruti Swift, Ford Figo and Hyundai i20.





How the fuels compare

First let’s take a look at the pros and cons of each type of fuel.

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Diesel and petrol are widely available fuels. LPG too has a larger network than CNG in India, because CNG requires large-scale infrastructure setup as it needs to be stored under pressure and piped to fuel stations.

When you look at the engines on offer in India, diesel engine give the best mileage, as their high-compression ratio (of 18:1 vs 9:1 for petrol) makes them use fuel more judiciously. CNG in India is used as an alternative to petrol. Ideally, if CNG could be used in a high-compression engine, it would deliver far better mileage as well, but it has a lower energy output – the lowest among all the fuels (hence the lack of power associated with CNG). LPG tends to give slightly lower mileage as it has a lower calorific value (amount of energy to burn) than petrol or diesel.

Which gives better mileage?


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Going by the nature of the fuels and looking at an average car, diesel cars give the best mileage per litre of fuel used. Approximately, if you look at an average car that gives 15 kmpl on petrol and assume the same car was converted to LPG – it would give about 14 kmpl. If it were converted to CNG it would give 16 kmpl. A diesel engine of similar capacity in that car would probably deliver about 20% more mileage and hence we assume about 17 kmpl.

Running cost of Petrol vs CNG vs LPG vs Diesel


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At the new diesel prices, that would give a running cost of 2.76 per km, compared to 4.56 per Km on petrol, a saving of Rs. 1.80 per km if you have a diesel car. Assuming you have a CNG car the savings are even more at Rs. 2.16 a Km – nearly 60% savings. On LPG though, you won’t save that much – only Rs. 1.51 per kilometer. In a month, if you run about 1000 km, the most expensive running cost is obviously petrol, followed by LPG, then diesel and the cheapest being CNG.

The savings that you make from each of these fuels – that extra money can be added to your EMI of the car. Approximately an LPG car is about Rs. 20,000 more expensive than an equivalent petrol car, a CNG car about Rs. 50,000 more (for a good sequential kit) and a diesel car about Rs. 1 lakh more (for a premium hatchback like the Swift). If you buy this on EMI on a five-year loan – it will mean an outgo of Rs. 2,250 a month for the diesel car and about 1,100 for the CNG car.

Return on investment


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Now let’s take a look at when you will be able to recover this additional investment. The more you run your car, the quicker your return on investment. (That’s why you opt for a cheaper fuel in the first place).

Taking the additional cost of a CNG, LPG or diesel car against that of a normal petrol car, you will need to drive about 23,150 km to recover the cost of installation of a CNG kit and about 55,600 km to make sense of your investment in a diesel car. Whether that happens in a two years or four years depends on how many KM you drive a month.



So is diesel still the most attractive fuel? In terms of running costs – no, CNG is the best fuel for running costs. In terms of a good compromise between initial purchase cost and running cost, LPG is a sensible fuel.

However, when it comes to availability and fuel efficiency, diesel is still the most widely available fuel and hence makes sense if you travel out of town a lot – where LPG and CNG is not available.

But if you are in a metro and do a lot of driving and want low running costs, then CNG is the most attractive fuel.