Petrol vs diesel vs CNG vs LPG.. Which one should you opt for?

Since the start of 2010, petrol prices have been revised 11 times going up from Rs 44.7 per litre in January 2010 to Rs 63.66 today, a whopping 42% rise. Diesel prices have suffered a change 8 times in the same duration, as prices have risen at a more humane 25%. While this widening gap between the prices of the two fuels has triggered a shift in the buying pattern of cars, a more informed and analysed approach is needed to determine which is an outright better option in the medium to long term. At the same time should one look at CNG and LPG as well?

Traditionally berated for being dirty and noisy, diesel has clearly emerged as the fuel of choice for the Indian market. Wherever a car is available in diesel and petrol, it is the former that outsells and the margin is only increasing. Even the Rs 80,000-100,000 higher price tag of a diesel car is no longer a deterrent as consumers reckon it ends up to be a better deal in the end.

But does it really make all that sense for everybody to ditch petrol and settle for diesel? Or should one also consider other options like LPG and CNG as well?

Diesel: fun, Petrol: power

Technological advancement has ensured that diesel today is a clean burning fuel that emits 15% lower carbon dioxide than petrol. Clearly, associating it with the black noxious fumes being exhumed by yesteryear’s trucks on state highways, would be a complete misnomer.

A diesel engine has a much higher compression ratio as it relies completely on it to combust the fuel unlike petrol engines which require external ignition by way of spark plugs. Because of this basic difference, a diesel engine is heavier by nature designed to generate compression ratios between 12:1 and 25:1. Petrol engines on the other need compression ratios only between 8:1 and 12:1.

For the lay consumer behind the wheel though, the difference between a diesel and petrol car is in the two’s distinct driveability. If a similar sized diesel and petrol engine is compared, like in the case of Ritz which is powered by a 1.2 litre K series petrol engine and a 1.3 litre multijet DDiS diesel engine, the former develops 85 PS power and 113 Nm torque. The diesel engine on the other hands belts out a lower 75 PS power but a much higher 190 Nm torque.

More power means the petrol Ritz is capable of doing much higher speeds while its diesel counterpart will start huffing and puffing at three digit speeds. The petrol variant however boasts of lower torque figures, once again a fall out of lower compression ratio. Torque is the force needed to rotate a wheel and the diesel variant’s higher torque ensures it is faster off the block and commands better acceleration. In city traffic therefore the diesel is more fun to drive as also in cases when a quick overtaking manoeuvre is necessitated on the highway.

Pros : Lower cost of car, refinement, power
Cons : Higher cost of fuel, likely to get even higher

Pros : Mileage, lower cost of ownership, peppier drive
Cons : Expensive technology, coarse and noisier, lower top end power.

The CNG-LPG factor

Consumers in some metros and other big cities today have the choice of CNG and LPG as well, and these are being offered by some manufacturers like Maruti, Hyundai, Tata and Chevrolet as factory fitment as well. They also have the advantage of being fitted from the market place on any car, a choice that diesel certainly lacks.

Due to the restricted availability of compressed natural gas, its growth is not talked about in the same vein as diesel. But wherever CNG is available, like Delhi NCR, parts of Gujarat and some other towns in UP, Haryana and Rajasthan, it has come up as a very strong competitor.

Globally as well, CNG is increasingly becoming a favoured mode of fuel. Outside the hybrid technologies, it is the cleanest fuel available with CO2 emissions, 20% lower than a conventional gasoline vehicle. It is also the cheapest at under Rs 30 per kilogram.

What also augers well for CNG is that there is no lack of availability of the fuel in India. India has the 7th largest reserves of CNG in the world though most of it is untapped and needs investment. It is without doubt the fuel of the future and once it is available in more abundance, its price, which is already lower than the others, would come down further.

One big factor against use of CNG as an automotive fuel used to be the lack of safety (cases of fire are still reported) and power loss that drastically reduced the pleasure of driving especially when the air conditioner is switched on. Further, in the case of small cars, the 20kg cylinder almost always takes away all of the boot space, a not too favourable prospect.

The first part of the problem however, has been addressed to some extent, with carmakers like Maruti introducing gas port injection technology. Since the modifications that include dual inter dependent ECU mapping, is done at the factory level, the cars are well tested for safety and also carry the manufacturer’s warranty. In the erstwhile CNG technology, the kits were retrofitted that automatically led to the annulment of the manufacturer’s 2-3 year warranty.

The newer technology has also reduced the power loss associated with CNG and these cars now have pick up and drive similar to that of a petrol car. Almost.

Automotive Liquified petroleum gas on the other hand is well past its sell by date and is unlikely to find much favour in the market in the years to come. It is not hampered by availability issues as much as CNG, but its price mirrors that of domestic LPG, a heavily subsidised fuel, and has risen the most in the last 20 years.

Pros : Lower cost, fuel of the future, lower emissions, very popular worldwide too
Cons : Boot space is compromised, lack of availability, serpentine queus.

Pros : Lower cost compared to petrol, better distribution than CNG, boot space only partially compromised
Cons : No longer a very cheap fuel

Who is the best of them all?

It takes a little bit of science and a lot of hypothesis to decipher, which fuel option would be the best in the medium term (say 3 years) to long term (5-8 years). Since 1989, petrol prices have been revised on 70 occasions, of which 54 times prices have gone up and 16 times it has come down. Diesel prices have been revised 73 times with an increase happening on 50 occasions and a decline 23 times.

In all these years that saw the Gulf Wars of the 80s and 90s, the East Asian crisis of late 90s, the 9/11 attacks and the consequent wars in Iraq and Afghanistan, the interminable battle for Jerusalem and the ongoing Arab revolution, petrol price has gone up by almost 8 times, while diesel has gone up by over 12 times. The increase in the price of LPG is even steeper.

This has largely affected the running cost of vehicles over the years. Considering that diesel is a fuel that is used widely by trucks that provide last mile connectivity in distribution and hence more internally linked to general inflation, it has seen relatively less volatility. It is also not decontrolled like petrol (last year) and hence would continue to be less prone to hikes in future.

Between the four options that are available to consumers today, a diesel car costs the maximum and a petrol the minimum. Between these two, CNG is the next most expensive followed by LPG.

However, due to its lower price and higher mileage, it is CNG with a running cost of just Rs 1.2 per kilometer that provides the most value for money followed by diesel’s 1.96 per km. As stated above, LPG is increasingly becoming a less attractive proposition with a running cost of 2.54 per kilometer, only a rupee less than a petrol car.

Diesel makes all the sense for a person who is a heavy user of cars. If somebody routinely logs 16,000 kilometers per year (national average is 13,000 kms), roughly 1300 kilometers a month, or 45 kilometers a day, a break even compared to a petrol car that would cost Rs 80,000 less could be achieved in a little over 3 years at current rates. If the person happens to drive the car for 2 more years at the same rate, he would end up with a saving of almost Rs 51,000 over a petrol car. The diesel’s case is almost similar to that of LPG, only that the latter would be less profitable if the car is kept for more than 5 years.

These numbers multiply almost 3 fold incase of a CNG vehicle. A break even could be achieved in less than a year and a half and in 5 years a saving of Rs 1.36 lakh could be made.

It is an open and shut case for those who stay in metros and have the luxury of availability of CNG, and do not mind the lack of a boot space. Driving 45 kilometers a day in a metro like Delhi, Mumbai or even Ahmedabad, is a routine affair for most. Those who do not have CNG yet, would have to settle for diesel, which it seems most are.

But those staying in mofussil small towns of the country, where driving even 10 kilometers means one is out in the hinterland, the psychology of saving that diesel gives every time one refills the vehicle is only a mirage. By the time you decide to do away with the car in 5 years after driving it for only 45,000-50,000 kilometers, you may not have saved anything at all. The good old petrol still makes sense and if perchance CNG does come calling in between, you would only be happier. Sadly, diesel and CNG don’t go hand in hand, and never will.

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