The Hindu Business Line : Gaining fuel efficiency

I would like to know the effect on mileage if I disengage the engine by shifting into neutral and lift my foot off the accelerator pedal, say, when on a down slope or before coming to a halt at a signal. The car does travel a certain distance before coming to a halt. Will this improve mileage? What will be effect of this on the engine, clutch, etc.?

K. Chandrasekaran

Shifting into neutral and letting go off the throttle ahead of coming to a stop at a signal or sometimes when going downhill can be a good idea for reasons other than gaining better mileage. The improvement in fuel efficiency may well be only marginal given the fact that the opportunity to indulge in this kind of a fuel saving exercise is limited.

But there will be other savings to be had by shifting into neutral, instead of riding the clutch. The biggest benefit will be lower clutch wear.

The most ideal positions for the clutch pedal when driving a manual transmission car are either it being fully depressed or not being used at all. Anytime that the clutch pedal is partially depressed, there will be clutch wear, in addition to `powertrain' wear. To that extent, quickly shifting into neutral and releasing both the clutch and throttle pedals can contribute to a bit of saving both in terms of fuel consumption and in terms of clutch wear.

But there is a point to be taken note of here. Every time that you are coasting in neutral, with the engine just idling, and you attempt to get back into a gear slot, there will be an element of clutch wear if this is not done right. Every gear slot has an engine-rpm range that will be the most ideal for ensuring low clutch and gear wear at the time of shifting and for ensuring that engine knocking does not set in.

If the engine rpm level is low for the gear selected, the vehicle will lurch and there will be powertrain wear. To avoid this, the average car user will tend to use the clutch for longer than is necessary to just shift into gear. This will lead to increased clutch wear and replacing it can be expensive. Training and practising to shift back into gear from neutral or from a higher gear at the right engine-rpm level, including, if necessary, using the accelerator to push up engine rpm will help avoid unnecessary clutch wear. This could be a good practice even during normal driving.

I am planning to buy an upper C segment car. I am totally confused between the Toyota Corolla H1/H2 and the Hyundai Elantra. I drive around 20,000-22,000 km a year. I am looking for a low-maintenance trouble-free car that will perform well for the next 6-8 years at least. The advantage the Elantra has is its value for money proposition over the Corolla. The petrol Elantra, however, offers poor fuel efficiency. So I was thinking of stretching the budget to buy the Elantra CRDi.

Then I came upon the news of the new Elantra launch in the US. With newer petrol and diesel engines and better looks. So I decided to delay my purchase, as I wanted to wait for the new Elantra? With my kind of driving, should I go for a petrol or diesel? How much is the maintenance cost difference between the two? Can we expect the new Elantra to be launched in India by February 2007? When comparing the Corolla, the new Elantra petrol/CRDi and the Mitsubishi Lancer Cedia Select, which one will make more sense?

Piyush Dikshit

The new Hyundai Elantra is unlikely to be launched in the Indian market in a hurry. So, unless you are willing to wait until the middle of next year, the current Elantra model will have to be the one that should be compared to the other two you have listed.

The Elantra's relatively poor performance in the premium sedan market means that the car's resale value will be lower than its more successful peers. The same market logic will apply to the Mitsubishi Lancer Cedia too.

With your kind of usage, the diesel variant will make practical sense in the long term. Hyundai's pricing, dealer offers and possible discounts will make the Elantra CRDi an attractive choice. So, if the resale value issue and the possibility of the car being replaced in six months to a year do not bother you, go ahead and choose the car.

But a better bet could be the Toyota Corolla's new Executive trim variant that was recently launched and priced below Rs 9 lakh (ex-showroom). The Toyota Corolla petrol is still a frugal burner and with Toyota's relatively better resale value, it may fetch a better price in the future.

Queries may be sent to: q&a@thehindu.co.in or by post to Q&A, Business Line, 859/860, Kasturi Buildings, Anna Salai, Chennai - 600 002.

K. Chandrasekaran

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