Whether Diesel or Petrol?

Preamble
During the last five years, diesel engine technology has seen phenomenal pace of development and turbo-charged ‘common rail direct injection’ systems have become order of the day, giving a full run for their money to their petrol siblings. So, let’s have a look at some typical QnA’s on the subject…

Question and Answer
As a Diesel Car is less environment friendly and has higher maintenance cost, would it not be prudent to get a CNG kit fitted in the car by a reputed manufacturer, even if it affects the warranty of the Car? Please advise. Does loosing the warranty matter much, especially if the car is from a reputed manufacturer? Do the latest Diesel Engines e.g. those of Maruti Swift, Logan and Ford Fusion, in the long run, make noise, pollute more, have a higher maintenance cost etc.? It’s understood that one should be doing 1500 km+/pm for a diesel to be ‘viable’.

For starters, with the state of art ‘common rail direct injection’ technology with ‘multiple pilot injection’ as found in the MUL/Swift-D, diesels today are actually MORE environment friendly AND ‘fuel-efficient’ compared to contemporary petrol engines. In fact, nearly 60% of new cars sold in the EU today are diesels! LPG/CNG are also good ‘green’ fuels but only petrol engines can be converted cost-effectively. Besides, their road side availability any where in the world, leave alone in India, is not as wide spread as diesel.

As far as losing warranty on engine is concerned, it’s far from advisable as if at all some thing goes wrong - the chances of which are bright in retro-fitment of Gas Kits into Mpfi’s, it can set you back by thousands of INRs’. Therefore, it’s a lot wiser to go for vehicles that come OE with such Kits - a number that’s growing steadily over the years.

As for engines of present generation diesel cars getting noisier over the years, a perceptible increase is inevitable due to wear and tear - just like the petrol ones - but other than that, if maintained ‘as per the book’, which is seldom the case with most car owners in India, no abnormal noise levels can arise. Once the warranty is over, people tend to be penny wise pound foolish by stopping from getting their cars serviced at the OE authorised service centres and instead, go to the friendly neighbourhood mechanics - not realising that the present day cars need special hi-tech diagnostic and servicing eqpt. costing lacs of Rs., not to mention the know how - something which the FNM’s can never afford to acquire or have.

Regarding higher maintenance costs as the vehicle gets older, it’s but natural and petrol cars are no exception. It’s one of the reasons why it’s recommended that one should be doing more than 1500 km/pm to ‘qualify’ for a diesel.

Question and Anwser
1. My diesel Zen has done 40,000 kms. It is in for servicing and they want to do engine de-carbonisation. Is it required?

1a) Strictly speaking, decarbonising at this stage/40 kkm is not called for on engines like yours but a lot depends on the quality of diesel fuel used. What you should ask your MASS is as to how they propose to do the de-carb. If it’s going to be by lifting the cyl head and mechanically scrapping the combustion chamber/piston tops’ deposits BUT leaving an about 3-5 mm ‘ring’ of carbon deposits around their periphery/cylinder walls, then it may be done. But on the other hand, if they’re going to do it by hooking on some m/c with solvents etc and then run the engine on it for 1/2 an hr or so, then it’s NOT advisable coz it can lead to some serious problems of loss of compression later on.

1b) In addition to above, the vehicle’s ‘exhaust line’ should be manually decarbonised. This can be done by taking it out completely, ‘tapping’ well the catcon and the mufflers with a rubber/wooden mallet to dislodge their internal carbon deposits and then flushing them out with high pressure water hose shoved in at the engine end till clear water starts flowing out of its tail end.

2. Do you recommend any more special work/check to be done during servicing, in addition to what is in the Manual?

2a) In addition to these, you should also ask the garage to change your ‘valve timing belt’ at this stage, to pre-empt its snapping in foreseeable future. For, if it snaps while the engine is running, it can cause a lot of expensive internal damage to an engine like yours. Unfortunately, such belts don’t come cheap - over Rs: 1,000/- but it’d be money well spent.

2b) Besides this, you should also ask your garage to reset the various/8-nos ‘valve clearances’ at this stage, as they’re bound to have reduced over the limit due to wear on the valve seats. If allowed to continue with such reduced clearances, burning out of exhaust valves in particular cannot be ruled out in near future - again an expensive and a cumbersome procedure to fix.