On my normal daily run there are long-term "temporary" traffic lights.

The wait is normally 3+ minutes and if you're unlucky you will not get through the first time. I would say 12 - 15 waits per week.

Question is whether to switch off the engine? Just sitting there engine on, handbrake on, in neutral the trip computer will drop from say 44 mpg down to 37 mpg, giving me ~ 7-10% reduction in MPG on the whole run.

Switching off and restarting saves fuel but means using the starter will perhaps shorten its life? (It will also use a very little more fuel recharging the battery but the trip computer suggests that this is trivial.)

Are those cars fitted with Start-Stop technology also fitted with heavy duty starter motors? Is what I am doing false economy?

When I was in the US I helped fit a kit to a GM SUV. The list of parts gives an idea of the problems.

It consisted of...

Uprated geared starter

Uprated battery

Uprated alternater

Heavy duty flywheel (the ring gear was much more substantial)

Uprated starter/alternator cable sets

Control unit

I would have thought the couple extra starts/stops for the OPs situation would hardly be noticeable in terms of wear on the starter etc. Just think how many times a car gets stopped/started in its life. Also taxis etc. which must stop/start the engine so many more times a day compared to the average motorist. Not something I would be worried about at a set of lights.

I would have thought the couple extra starts/stops for the OPs situation would hardly be noticeable in terms of wear on the starter etc. Just think how many times a car gets stopped/started in its life. Also taxis etc. which must stop/start the engine so many more times a day compared to the average motorist. Not something I would be worried about at a set of lights.

True. In the OP's case it would make very little difference. It's no different to stopping off for a paper on the way to work. The stop-start technology is different and may need to restart two or three times when moving up to a set of single file roadworks.

worst case scenario in about 5 years you might need to replace the starter I would imagine, cant see it being a problem, 24 extra starts a week isnt that much, as someone said compared to a taxi.

From what I've read, stop/start systems are more complex than just having a heavy duty starter and battery. e.g. starter motor is built into the flywheel to eliminate the Bendix gear.

Think the current Auris is like that.

From what I've read, stop/start systems are more complex than just having a heavy duty starter and battery. e.g. starter motor is built into the flywheel to eliminate the Bendix gear.

Think the current Auris is like that.

Cars that are designed with this function (ISG) do indeed have an integrated starter alternator. The starter and alternator are the same thing and as it is permanently connected to the engine, when it is not starting the car, it is charging the battery.

I've often wondered this, and like the OP, I turn my engine off if i'm going to be stationary for a wee while. Pressing your clutch pedal in when you start the car, as is being suggested in the "First Impressions" post, may put less strain on the starter motor, thus reducing wear and tear on it. I'm defo going to try this, because I can't see any point in saving fuel cost if it means that i'm going to have to fork out for a new starter motor later on down the line.

I can comment from direct experience with a Diesel re the fuel savings from "stop start"

For a wee while I amused myself attempting to get the max mpg with general normal mixed driving.

Smooth acceleration, anticipation, no heavy braking etc etc, but otherwise driving at normal speeds.

I then started switching off at the lights or when stopped after I had established a reasonable "benchmark".

It made a noticible difference to the mpg.

However I have replaced the starter several times (but not always due to this practise)

but origional flywheel at 225,000, & only on the second alternator & third battery.

cheers

M

Edited 13 September, 201015 yr by dieseldogg

Used to be spoken that if you stop for 30 seconds or more then you'll save fuel by turning your engine off.