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I want to purchase hatchback and since last few weeks I am researching on it. Like all other beginners, at showroom, I also faced following questions.

  1. Petrol car or diesel car?
  2. 3 cylinder or 4 cylinder?
  3. What are the criteria in selecting car?

I surprised all showroom asked same question. What is the reason behind it? Let me answer what I learned from my research.

Question 1. Petrol or Diesel?

Before starting we must know following things about car

  • Each car has some Initial Cost (IC)
  • Each car runs on fuel and thus Running Cost (RC) is involved
  • Each car requires maintenance and Maintenance Cost (MC) is involved

Unlike European countries, India has huge difference in petrol and diesel prices. Technology of diesel engine is costlier than petrol engine and maintenance cost of diesel engine is 40% more than petrol engine. Why so? Irrespective of fuel used, in any car, chasis, tyre, steering, seating etc are remains same. The only difference comes in the engine. Petrol has carburettor while diesel has fuel pump. Fuel pump will have more freiction due to its moving nature and hence wear and tear will be higher in diesel engine. Also, diesel car will have higher torque and its break bush will wear more far the same brake used in petrol. That is why diesel car has higher maintenance cost.

Before proceeding further let assume following things.

  • Maruti Suzuki Swift (ZDi/ZXi) model is considered in this study.

  • Assume car runs x km.

  • Servicing has to be done at 2 years. Hence, MC is not counted in costings.

Let’s look at costings. You paid some initial cost, you are using fuel, and you are servicing your car. Summation of all these costs is known as Cumulative Cost (CC).

CC=IC+RC+MC

RC=Distance Travelled (km) * Fuel Cost (₹/lt)/Mileage (km/lt)

CC=IC+x*FC/Mileage

Car (Maruti Suzuki)

IC (₹)

FC (₹/lt)

Mileage (km/lt)

ZXi

7,09,162

72.94

20.4

ZDi

8,27,229

57.23

25.2

At first sight, a common man will be confident for selection because

  • Diesel is cheaper

  • Diesel gives better mileage.

  • Diesel model is costlier.

He will think

Despite of higher IC of diesel car I should purchase diesel car because it gives better mileage and its fuel cost is lesser

He is wrong here. Over a period of time, depending on your usage, diesel car could cost you more.

CCp=ICp+RCp

=709162+x*72.94/20.4

CCd=ICd+RCd

=827229+x*57.23/25.2

Let find Break Even Distance denoted by xbed, where CCp=CCd

709162+x*72.94/20.4=827229+x*57.23/25.2

xbep=90510 km and CCp=CCd= ₹ 10,32,780.9

If

x<xbep then CCp<CCd

x=xbep then CCp=CCd

x>xbep then CCp>CCd

This means if your monthly usage is 200 km then it will take 37.7 year (90510/2400) to reach xbep. Till then petrol car will be cheaper to you!!! This is explained in graph below where blue line is for CCp and red line is for CCd.

Cumulative Cost for Petrol and Diesel

Cumulative Cost for Petrol and Diesel

So, in such a low usage it is not advisable to purchase diesel car. It is advisable to purchase disel car if you are running 30 km daily which will take 8.4 year (90510/30*30*12) to reach xbep. In this case diesel car will be economical between 9th and 15th years of usage since cars are given maximum 15 years of road permit.

Let me write xbep for some of the poppular hatchbacks.

Chevrelot Sail UVA(LT ABS) 66300

Skoda Fabia                       54804

Volkswagen Polo (highlin)   52371

Fiat Punto Evo (Emotion)    46666

Tata bolt (XT)                    40587

Ford Figo (Titanium)          34911

Summary on question 1

Let me summarise, if your usage is lesser which is typically for house hold then go for petrol. If your usage is 30 to 40 km per day then go with diesel car.

Note: You will be curious about:
3 cylinder or 4 cylinder? Why many of the European car manufacturers (like VW polo, Skoda Fabia, Chevrolet Beat etc) are now a days designing 3 cylinder engines? Wait for next blog.

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