After watching TG last night it got me thinking.

I sometimes coast to a stop when I can see the lights are red in front of me.

Does the S2k use petrol when on overrun?

 

No.

The last cars that did this would have been the early injection cars (early 90s, maybe some later cars with older design) and, obviously, cars with carburettors.

 

that was an interesting point and has been raised many times, although of course the engine braking effect will use 'energy' and so coasting will get you more mileage for the same stored energy....

Although of course you have less control should you need to stop quickly or react to something....

coasting on the whole is not recommended, but in terms of pure economy is better than allowing the car to come to a near stop whilst in gear....

thats what I understand anyway....

 

So it doesn't use petrol in gear or out of gear?

I sometimes take the car out of gear in traffic, going down hill. Is this bad?

 

It uses petrol out of gear to keep the car idling

 

If IN gear and coasting down, the car will use no fuel.

If OUT of gear (i.e idling) and coasting down, the car will use fuel.

Needless to say, in both examples the clutch pedal is NOT pressed down.

If car is IN gear, you will have more control - say a car/cyclist etc. coming from a side road looks like it's not going to stop, a quick blip of the throttle and you can get ahead so they fly into the road just behind you - yup, I've had this happen. If I was coasting out of gear, by the time I'd got it into gear and accelerated, it would have been too late and he would have hit my rear wheel/wing.

 

As said, if you coast out of gear, the car will use petrol to stop the engine stalling.

I always leave it in gear for as long as possible, its good practise too, gives you better control and if it is at all measurable, save's fuel.

 

Thanks

 

Interesting, so engine breaking aside, leaving ingear is more economical than coasting?

I stand corrected.

for pure ecomony then, leaving in the highest gear possible to minimise engine breaking is best, although nearly as 'less' responsive as coasting...

 

You have to judge it on road conditions etc., remember, safety first.

In "pure" economical terms, it doesn't matter which gear you are in when coasting down in gear. In a higher gear you will have less resistance and will coast further, in a lower gear the car will slow down more but you will have more response if you do need to accelerate.

Also, once below about 1500rpm the car will need to inject fuel to prevent stalling so don't try leave the car in 6th at 15-mph!