Among the numerous factors influencing one's carbuying decisions, it's the hard choice between the refinement of petrol engines and diesel engine's frugality and torquey character that leads the research further. While on one hand, petrol engined cars are cheaper (in most cases) to buy than respective diesel engined versions, the lower per litre cost and better fuel economy of the latter often gives a perception that if you want to save money, running on diesel is the way to go. It's time to get some more clarity on the topic, don't you think!
Let's start with the buying cost. Looking at similarly specced versions of diesel and petrol versions of the same car, it's easy to decipher the pricing strategy. The diesel versions are generally costlier, with the difference often lingering in the Rs 1 lakh range for most cars on the right side of Rs 20 lakhs. Now it's given that the diesel variant will get you a better range and economy, but in order to justify its higher sticker price, it would take about about a year and a half to equalize the costs (if you're running close to 50 kilometers in a day).
The second thing that worries the prospective diesel car buyers is relatively high NVH levels and maintenance costs. Now, in comparison to petrol engines, it's no denying that diesel engines sound a bit harsh, almost on the verge of being called agricultural, but that's on the outside. Modern day cars do a decent job in minimizing the engine noises entering into the cabin to a level that on a busy day, it won't occur to you that you're in a diesel. On the other hand, petrol cars are silent and more refined, which works to a great extent in their case. As far as maintenance costs are concerned, diesels are still slightly on the costlier side but not by a huge margin.
On the driving front, comparing the two is simple. While one offers great low down torque and ease of use (which in this case is the diesel), the other offers a good amount of power in high revs and is more responsive to driver's inputs (petrol in this case). Having said that, it must also be noted that the line between the driving characteristics of the two engines is very thin. So, unlike in the earlier days of diesel engined cars, you can now spend hours in stop-go traffic in either of the two. Diesel vehicles are more suited for trips on the highway, thanks to the fuel economy and since they have a lot of torque available in the lower rpm range, you don't need to keep revving them. Petrol engines are still favoured by enthusiasts, thanks to their responsiveness and power delivery. Choosing one between the two comes down to what you want from your vehicle, outright high-revving driving fun or a mixture of fun and practicality.
Longevity of diesel engines is perceived to be lesser than the petrol versions, which is not right. Current day diesel engines stay as healthy as petrols, as long as they are serviced on regular time intervals. So, that shouldn't be worrisome either.
Now all that brings us to the final and the most important question: Which one to buy?
If you look at just the buying and running cost aspect, then it's the diesel winning hands down. To justify the regular price difference over a year or so, a monthly run of about 2,000kms would do the job. If your monthly commute comes anywhere between the 1,500 and 2,000km mark, diesel's the easy choice. Anything less than that, and petrol engined versions make more sense. If you intend to keep the car for a long period of time, then diesel's frugality will keep the fuel bills light too
But don't write off the petrol engines just yet. Although they don't offer as much of savings that a diesel would, the refinement of petrol cars make driving them an enjoyable experience. They are peppy in the city and thanks to linear power delivery, they won't give you a sudden burst of power that a turbo-diesel would. Also, the buying costs for petrol cars is less than their diesel counterparts, and that could work for you in case you're on a budget. With CNG kits on petrol engines, you can enjoy great fuel economy as well. That way, you won't just be saving money but the environment too.
Another important development in petrol engines is the use of turbocharging, which not just helps them make more power, the efficiency increases as well. Cars like the Volkswagen Polo GT TSI, the Ford EcoSport EcoBoost, Skoda Octavia 1.4TSI etc use the technology and return respectable fuel economy.
Calculate your monthly commute, look at various cars in your budget (diesel, petrol, petrol+CNG, and turbo-petrol), and then decide which one suits you and your requirements the best.
If you already own a car, here are 5 easy ways to improve the fuel efficiency of your car