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Old 17th December 2007, 19:56   #1
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Default The Technical Truth? :Petrol vs Diesel

My Query
For long i have been wondering Why exactly are diesel variants of the same car more expensive than the petrol one
to a layman like me i would feel that everything except whats under the hood remains the same so why the 70-80K price diff?
Now i know you would say - that all thats "under the hood" is what matters but what i cant seem to justify for myself is that why such a big price differnence: Now i diesel engine is made from the same alloys as a petrol one correct? ( its not like its made of platinum or rare alloys!), yeah i guess te fuel intake, etc etc differ but why this difference ( i mean 60-80K whats the justification? i mean why not just 20-30K?Cant the diesel engine parts be manufactured in that much extra ? - Being in a manufacturing industry myself i know 30-40 K should go a long way for bettering ANY kind of part)

Can you enlighten me about the real technicalities behind this
(Pardon my NOOB query)

best regaurds
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Old 18th December 2007, 00:48   #2
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The bulk cost is due to fuel pumps and injectors. Then you got turbocharger, cams for fuel pumps or timing device (ECU), heavier camshaft or drive for fuel pumps (due to very high acceleration of fuel pump plunger for high injection pressure) etc etc. Also combustion products of diesel are more corrosive than petrol, the valves are of slightly different alloys.

Last edited by jat : 18th December 2007 at 00:51. Reason: Also extra profit due to people's attraction to diesel economy.
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Old 18th December 2007, 00:58   #3
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dont diesel engines have high compression.? check the prices for aftermarket high compression stuff for petrol engines.
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Old 18th December 2007, 01:21   #4
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IMO, the price differential (such a huge gap) between petrol and diesel is not warranted nowadays. In the older vehicles, petrol engines used to be much simpler, with fewer mechanical parts ,Lesser compression meant lighter blocks,also diesel tolerences were more tighter.

If you count the number of mechanical parts that goes into a diesel injecting system you will appreciate that.In comparison, the carb was a piece of cake, and not to mention it had the advantage of popularity and scale.

But nowadays, the same gap is supposed to close down because:
1. Increased popularity for diesel engines
2. Increased complexity for petrol engines (MPFI Vs CARB)

However it is not happening so,because the Manufacturers would also like to enjoy the premium commanded by the diesel .....It's as simple as that.
So basically its not only Production/Technical reasons but also economic considerations that make manu. to claim a premium for diesel vehicles. But then if customers are willing to pay the premium then what stops them?

From the point of view of the customer, he can enjoy better FE and Engine life(heavier, tighter, stronger) and/or resale value, who will complain?

Skoda is one manufacturer who broke that trend in india by offering diesel engines at no extra-premium, and its evident that it payed them off well.

Well i tried to put things
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Old 18th December 2007, 07:43   #5
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Quote:
Originally Posted by aravindwarrier View Post
Skoda is one manufacturer who broke that trend in india by offering diesel engines at no extra-premium, and its evident that it payed them off well.
OT - The other way could also be true. The diesel is sold at a premium, with the petrol at an even higher premium .. but then the petrol might actually be more expensive and at par with the diesel prices since it's a turbo setup.

Last edited by shuvc : 18th December 2007 at 07:48.
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Old 18th December 2007, 08:26   #6
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Quote:
Originally Posted by aravindwarrier View Post
Skoda is one manufacturer who broke that trend in india by offering diesel engines at no extra-premium, and its evident that it payed them off well.
remember the octy diesel is not a crdi. i think the cost would have gone up by the 70-80k had it been a crdi. even the superb diesel is more expensive than the petrol.
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Old 18th December 2007, 09:18   #7
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Quote:
Originally Posted by shuvc View Post
OT - but then the petrol might actually be more expensive and at par with the diesel prices since it's a turbo setup.
Well the diesel also, in this case is a turbo !.
And as you sugggested RS commands a premium not only because of the engine but also because of the other goodies thrown in.
You take any other car, Like the Lancer (not cedia), the premium that the diesel used to command over the petrol was not really justifiable.

But then definitely there is some higher cost incurred in the manufacturing process, otherwise Tata could never have priced Xeta that cheap.But then in the same vein ,their diesel is decidedly more preferrable compared to petrol
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Old 18th December 2007, 09:24   #8
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Well. Apart from the additional parts which makes the diesel cars expensive, I feel the manufacturers are putitng a premium for diesel cars as it will be giving you a better mileage and a cheaper running cost. remind you that diesel is cheaper than petrol by around 10-15 rupees. One of my friends has a Diesel indica. He gets a mileage of around 17kmpl. Whereas the petrol variant of Indica gives 11-12 kmpl.

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Old 18th December 2007, 09:42   #9
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Fuel Pump of a CRDi engine is what creates the majority of price difference...

Last edited by kpzen : 18th December 2007 at 09:43.
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Old 18th December 2007, 09:52   #10
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<frustrated sarcasm>
This is called marketing. CoMmOnerS like you and me will not understand this. Only guys and gals with an MBA in marketing will understand the secret.
The secret being when people are prepared to pay a premium, do make them pay; and how???
Else, what will M-S loose by putting a 5 gear box in the M800?
What will they loose by putting a 1L engine on the Alto?
What will they loose by putting better features like cig lighter, audio trays, hold for audio in the doors etc. in the WagonR?


In the frist version of the Indicas, the engine blocks for both the petrol and diesel version were same (the engine was a 1.4L thing then). I really do not think there is any justification for charging a premium of more than 5% on that design, but the premium was say higher then, and now.
</sarcasm>
BTW, diesel engines cause more vibration, and hence require stronger shocks and better anti-vibration mounts. And the engine bay needs better insulation from the passenger compartment.
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Old 18th December 2007, 09:58   #11
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Quote:
remember the octy diesel is not a crdi. i think the cost would have gone up by the 70-80k had it been a crdi. even the superb diesel is more expensive than the petrol.
Octy is TDi which is the same technology as CRDi,Isnt it? Different companies use different names. Like Mahindra uses CRDe, Toyota D4D, Ford TCDi, GM TCDi, Maruti DDis etc.
I feel that its the premium is beacuse of the demand/perceived demand for diesel engines. Yes, the added costs of turbo, fuel pumps might add to that. I feel the difference is reduced with time - like an accent petrol and diesel had a difference of Rs 2 Lakh.
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Old 18th December 2007, 10:13   #12
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but servicing cost of diesel car's is almost double than pertol once ? also spares are costly ? so i guess at the ned of teh day eveything comes to saem right ?
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Old 18th December 2007, 10:18   #13
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Quote:
Originally Posted by akshay1234 View Post
remember the octy diesel is not a crdi. i think the cost would have gone up by the 70-80k had it been a crdi. even the superb diesel is more expensive than the petrol.
Quote:
Originally Posted by abhilashvk View Post
Octy is TDi which is the same technology as CRDi,Isnt it? Different companies use different names. Like Mahindra uses CRDe, Toyota D4D, Ford TCDi, GM TCDi, Maruti DDis etc.
Octy diesel may be named TDI but the technology is at par with CRDI and in fact more advanced since it uses high pressure unit injectors that must be incorporated in the engine head design itself. In case of CRDI, the CRDI pump can be fitted to ordinary diesel engines also for eg. Tata 407 pushrod engine was upgraded to Safari Dicor 3.0. Of course, CRDI-ing an ordinary engine would necessitate a few other modifications too: providing for ECU, strengthening the engine parts to handle the additional power and torque, etc.

The technology actually is high pressure fuel injection and CRDI is only one example of it. CRDI is more common and popular simply because it permits upgradation of old, ordinary IDI/DI engines. Octy type engine is more complex and has to be designed from scratch.
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Old 18th December 2007, 10:30   #14
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direct injection - you sure your not confusing tdi with pump duese (pd)? i think it is the older type of diesels with a turbo before common rail.
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Old 18th December 2007, 11:06   #15
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Quote:
Originally Posted by aravindwarrier View Post
Well the diesel also, in this case is a turbo !.
And as you sugggested RS commands a premium not only because of the engine but also because of the other goodies thrown in.
Nah. I wasn't considering the RS. I was referring to the similarly specced Rider TPi and the Rider TDi, which cost almost the same.

Also most of the other comparisons of petrol vs diesel variants of the same model have either a CRDi or a Turbo Diesel. However in ALL those cases, none of the petrols are turbo's. Hence maybe a price difference.

In case of Skoda, both are Turbo engines - hence maybe no price difference. So what I was trying to say is - Skoda may not have brought the diesel version prices down to petrol version prices. They may have brought the petrol version prices up to the diesel version prices.
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