The idling rule is fine for naturally aspirated petrols. For turbo petrols and turbo diesels, it is unwise to switch off the engine if you're idling for less than a minute and a half. That's because switching off the engine would cut lubrication to the turbo, and since you're in city, the temperatures can have a very drastic effect on the cooling lines. Not to mention the apparatus itself.
Besides, if you start a turbo petrol/diesel after shutting it off, you again need to let it idle for 30 secs before moving off.
Therefore, in case of turbo petrols/diesels, if the countdown timer shows a minimum of 300 seconds (5 mins), then you can shut off the engine after 60 seconds (when the timer shows 240), and restart the engine when the counter shows 60; thereby effectively saving fuel for 180 seconds, or three minutes. Antything lesser than 140 seconds on the counter, and it isn't worth switching off the engine.
The factor to keep in mind is that the damage to your engine components due to repeated cranking at signals might offset the fuel costs you save. Therefore, saving fuel at traffic signals is something to be taken cautiously.
The ultimate solution is- if you reside in city, have to face a lot of traffic, and commute 30 kms or thereabouts to your workplace- then get a Reva as a second car. The savings in fuel costs (at about 1200 kms+ per month, you do the math- with an avg. F.E of 9 kmpl in city, you save about 7K) and engine components wear and tear will see you save enough money to cover the costs of Reva within a couple of years.
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DAD |