idling versus shutting off at lights

[carpenter_jai]

Hi All,

I'm sure this is a frequently discussed car topic, and I'm curious to see what the peeps here have to say.

I have heard that the amount of gas it takes to start a car is about 20 seconds of idling. It is therefore logical to shut the car off at most lights, ignoring wear on other mechanisms, such as the starter, to save gas.

However, we can't just ignore it, it does wear down faster. Anyone care to comment? Anyone disagree with the 20 second figure?


Jai

[Mike_Van]

I've read 30 seconds, but you're probably right.

If a light turns red just as I approach, and I know I'll have to wait more than half a min., I generally do turn off the ignition (and shut off all my accessories to allow the easiest possible restart).

Some hybrids and the VW Lupo 3l (not available in North Am.) will turn off the engine at a stop/zero load and restart when the driver releases the brake, but this may only work with auto transmission. Think of all the fuel we'd save if more people did this, especially at RR crossings. Having traffic lights like in Germany where a yellow+green preceeds the green would help to keep people from being caught off-guard with light changes...

-Mike

[geozukigti]

Sounds like a good way to ruin the starter, and the cables. The starter has no way of cooling itself, and it gets hot real quick. It takes a while for it to cool down, because it has no heat fins, nor a fan.