Auto Start/Stop - has anyone compared mileage with and without?

[Sabs]

I do a fair amount of city driving. I'm wondering if this feature will make a difference at stop lights.

Has anyone tried going a tank of gas with and a tank without this enabled to see the difference?

My driving isn't quite consistent enough between city/freeway on a tank to do it myself in the short term.

 

[SteveCo]

I don't think you could gather any meaningful data from comparing two tanks of fuel. Testing would have to be done under controlled conditions which could reproduce exactly the same conditions for each mode, which the manufacturers are capable of doing.

Obviously a car burning fuel while idling is consuming more vs. one that is shut off. So the question becomes how long must an engine be stopped before a restart consumes less fuel than keeping it running? I've heard that it's only a matter of a few second for a warm engine, especially with computer controlled GDI, so based on my driving and my average time stopped I believe I am saving fuel by using it.

 

[MerlintheMad]

If you drive the same route every day, this should be eminently doable. So, somebody needs to do this "for the team". Not me. I turn ISG OFF. But, I am interested in the study, for science.

 

[SteveCo]

I don't think it's possible to even come close to replicating the total amount of work, acceleration rates, etc. asked of the engine, much less the same amount of idle time, from one tank to another.

 

[HerbieTheCar]

Engineering Explained did a great video on how much gas idling can waste:

 

[Stinger @ JSC]

Personally I think the ISG is not a very good idea, it's hard on the battery, starter and other electrical parts. Please correct me if I'm wrong.

 

[SteveCo]

Engineering Explained did a great video on how much gas idling can waste:

Good video - I've seen that guy before, he's put out some good stuff.

So there are some empirical numbers - roughly 7 seconds of idling uses the same amount of fuel as restarting the car - idling longer than that is wasting fuel (tested with a four cylinder, but should scale pretty closely as displacement goes up).

City fuel savings using two identical cars running exactly the same route in real world traffic, one behind the other at the same speeds - 4 to 8.7 percent. Pretty decent saving ...

 

[SteveCo]

Personally I think the ISG (Idle Stop and Go) is not a very good idea, it's hard on the battery, starter and other electrical parts. Please correct me if I'm wrong.

The components involved are engineered for all the extra start/stop cycles they will be doing. Bigger battery, higher capacity alternator, totally different class of starter, etc.

 

[Stinger @ JSC]

The components involved are engineered for all the extra start/stop cycles they will be doing. Bigger battery, higher capacity alternator, totally different class of starter, etc.

Good to know, thanx for the correction.