PETROL V/S DIESEL: COMPREHENSIVE COST BENEFIT ANALYSIS

Isn't these premature failures (not the same parts but different) present in Petrol post 2000.

Most of parts are not serviceble but workshop replace them. This hold true to petrol and diesel vehicles. 

One would accept the fact that diesel cars have few more parts than the petrol ones but there are certain parts which are present in petrol and not in Diesel. Having said this, premature failure is not only issue in diesels but also in petrol and this is a recent phenomenon. In order to make cars more fuel efficient and agile, companies replacing parts with light material and sometime made of thin sheets. 

Failures are unfortunate and can occure to any make and fuel type. 

If diesel and petrol are priced at same level, still deisel will have lower running cost but yes TCO will be higher but then companies will reduce the price differential which exists at present

As per my information, these fragile parts have been added to diesels (post 2000) for two reasons:

1. To make diesels perform as smooth and easy as petrols while extracting more and more power from them.

2. Reducing emissions.

For e.g.

1. Dual Mass Flywheels reduce vibrations over the drivetrain and allow for far lighter clutches. Petrols donot need them in first place at all. Earlier diesels were notorious for heavy clutches and vibrating gear levers, making them pain to use. Even now, if there is a car with vibrating gear lever (e.g. verito) it points to use of much more durable solid mass flywheels.

2. Turbo and Intercoolers have been added so that more power and torque can be extracted from a smaller diesel engine. For e.g. Mitsubishi lance diesel in India has a 2 Litre diesel engine (no turbo and no intercooler - a bulletproof engine) outputting a meagre 68 bhp (~approx not sure of exact number) whereas my verna a 1.5 Litre engine outputs 110 bhp (with a costly Varaible Geometry Turbo and an Intercooler). Even FIAT 1.3 L multijet in SX4 is a 90 bhp motor due to VGT. No need of these devices in petrols.

3. Modern diesels employ common rails which work at extremely high fuel pressures of about 1500 bars (petrol injection pumps work at hardly 2 - 3 bars). I still remember that during one of my Verna's services, I asked the SA to show me the parts price list (of both petrol and diesel verna) and I was surprised to see that petrol fuel pump(or injector - not clear) was costing Rs. 4000 /- and corrosponding diesel one was costing more than Rs. 40,000 /- . Thats 10 TIMES MORE. (Other stuff like clutch plates etc. sported a similar pricing difference i.e. about 10 times) Due to these high pressures, common rails are very susceptible to bad fuel quality. Injector and pump failures are most common with bad fuels.

Earlier diesels were working with much lower pressures, employed simple technology and thus were somewhat tolerant to bad fuel.

4. Other stuff like EGR, Diesel particulate filters have been added to reduce the particulate and NOx emmisions from diesels as required by Euro 4, 5 and 6 (and  corrospondingly BS4 and later on BS5 and BS6). NOx and particulate emissions from a petrol motor are negligible. Thus almost no need of them in small size petrol motors.

Petrol technology being used by most manufacturers has become very mature and has not changed much in past 20 years resulting in very robust as well as cost efficient engines. If you are going for a petrol car - its the case that you can opt almost blindly for any petrol engine. They are bound to be reliable (I am excluding VW TFSI and FSI petrols, they are ultra mdern and require RON 95 petrol which is not available in India as such).

I feel it will take a bit of time when common rail technology will come a bit of age in performance as well as reliability at reasonable costs.     

Looking at the discussions, I feel that one should give maximum importance to the reliability of the engine rather than the mileage if we are going for diesel engines. Else the marginal saving due to high FE (I am comparing within diesel optios, not petrol) will be eaten away by increased maintenance cost. So, instead of going for the latest & greatest technology, one should go for the most reliable & proven ones (eg: Toyota). I guess this is what Sankalp was also conveying earlier, in this thread.

Tomy

@ Sarthak,

That was very elaborate and detailed explained technically and otherwise. 

Now manufacturers are going further with 1L diesel engines such beat. Globally engines below 2L are dominated by petrol and above 2L are diesel because of reliability issues. 

There are cars with low HP with higher engine capacities such as Lancer and in new generation hatches, such as Figo, Micra, Liva, Pulse have 1.4-1.5 L engine against the other hatches with National MJ Engine with 1.3L. This might result in better longevity of engine. 

@ Tomy,

Couldn't agree more with you. Reliability is paramount than FE.

One particular point still puzzle me; how to judge reliability of small engines, yes toyota is king of reliability when it comes to bigger size engines and sincerely hoping that holds true to liva as well. 

My take on reliability:

1. Engine Size: bigger side which might be low on HP.

What else. Guys how will be place hatches in terms of reliability particularly because cars with engine 2L or above have proven track record. 

If you really want to compare the reliability of an engine, you have to let it run under a taxi company. Only then you will learn how reliable the said car or its technicals are. When it comes to personal experience, I had a swift which was used and abused for 110k kms, with a pete's box. Other than wear and tear parts, nothing major was replaced. Once struts were replaced at 80k kms, which lead to around 8k rupee expense, but rest was fine.

Also there are two people whom I know having 1.6l odd and 2.1l kms on the Odo. The second car underwent turbo replacement. Rest was fine. I think that is the maximum one can run a car before selling it off. There is a Figo of a friend which is nearing the one lakh mark, again with no major maintenance other than W&T. Also, when it comes to the renault engines, you can ask any meru cab owner! He will swear by it.

The only diesels I have heard of developing problems early are the Accent CRDi, and the famous Dicors of Tata. The Indigo DICORS have a habit of making frequent visits to the service station for various problems, sometimes related to the Injectors, or cooling issues, etc. This makes any taxi driver fear a DICOR car. Hence they stick to the IDI engines of the old-Indica. 

The Etios also will last IMHO, but again there are quality issues with the car, so not sure. 

When we take the expenses to account, it entirely depends upon the condition the vehicle has run and the abuse done to it. Factors such as bad fuel, rough driving, irregular maintenance can even kill a toyota diesel also. So, the way you maintain is very much important. There are turbo failures in the early stages of a car itself, due to improper idling practice and hard accelaration. Such things also decide how much money you would be spending on the car.

Very true about the taxi runs. FIAT Multijet is an internationally renowned engine for its reliability. And Ford TDCi is a long termer too. Thats what I have stated earlier. Relaibility of an engine is a fuction of quality that the manufacturer puts in as well as how it has been used by customer(also its maintenance). Size is irrelevant.

Technologically simpler engines always make more sense that very much tech filled engine.

Etios uses the corolla powertrain. Should be bulletproof.

Sankalp, I am also looking for a new car and Etios is under consideration. What are the other quality issues that you are mentioning? 

I guess Etios will  not have any quality issues related to major parts lik engine, gearbox, chassis etc.

Most of the complaints I heard about Etios / Etios Liva is related to some cost cutting they tried on the body and accessories - thin metal for body (lighter), plastic parts not so good etc. Probably due to these, the cabin noise is also heard to be higher.

My friend who owns an Etios Liva was telling me that the 2nd gear is optimized for mileage and not for city drive. Hence we need to go to 1st gear often to avoid stalling of engine at low speeds. Not ture if it is same for Etios. Anyway, for diesel variant, I guess this will not be an issue since it has higher torque.

Tomy

Think Tomy has said it. While the Corolla and the like are international platforms, the Etios was kind of made for our country. So, there will be some difference in the construction, equipment etc if not the Engine. You could buy the Diesel but do enquire about the spare parts. A set of brake pads for my altis costed 16k rupees. Thats something to worry about even for me. 

Personal cars generally doesn't run more than 2.5-3 k/month in most case, which add to 1.5- 1.8 L kms in 5 years and people then tend to replace car.

I saw a Meru with something 2.6L +kms on odo and was in good condition. Once I visited Palika Bhawan opposite to Bhika Ji Kama palace, and had a chat with taxi stand guys, he told he change the engine oil and filters himself and never visited service station and car are running good.

These facts are testimony to the reliability of diesel engines with sone odd lemod car which can be true for petrol. 

Primarily everything boils down to how one is using car, idling practice, driving style, servicing particularly engine oil and filters (fuel and air), and fuel bunk. 

Dear Brandoo,

It was very interesting to read your comparisson between Petrol and Diesel cost analysis.

I have a doubt, you have at the end added up the cost difference in the cost of car, interest and the difference in maintainenece cost and divided by 5. When you have calculated the running cost for five years why have done ths for one year/

Moreover if you are considering the interest, why are you taking into the cost difference ie Rs 90,000? So I feel you should be adding up the interest and maintenece cost and reduce it from the diesel running cost. End all you still get a positive figure, but not so much as you got.

Please revert if I am wrong.