Start stop exists because on the standard NEDC test cycle it gave material savings in fuel consumption and emissions. In typical real life the savings are much smaller, one of the reasons that many cars do not get near the official figures. It's a sham.

I'd rather not have the added complexity, and probably extra weight, for negligible savings.

Stop Start is far more intellegent than it used to be but its still not perfect. Early versions (Citroen/Fiat?) should ahve been called Stop Stop since they did not monitor the battery and in many instances the car would not restart.

We have had Stop Start on 5 cars now, a BMW, a Nissan and 3 VAG cars. On the BMW and VAG cars its worked pretty much as you would expect but the Nissan in truth was pretty rubbish, very rarely did it work more than a couple of times even after a long run. Prefer that to not restarting though.

With reagrds to protecting turbo's I would say that VAG have this covered. After a 130 mile M6, M61, M60, M621 M1 trip on a abnormally hot summers day Stop Start was disabled until the oil temp returned to 90 degrees, it was 96 degrees when I left the M1. Probably took a couple of miles. In normal weather the oil temp never gets above 90 even on that trip.

But its fair to say even though it saves b***** all petrol its got to be better than sitting at urban traffic lights with the engine belching out fumes.

I can't compare with other cars, as my Mazda CX-5 petrol is my first with stop-start, but I have to agree it re-starts very promptly indeed. There seems to be minimal intervention from the starter motor and if you engage gear as you depress the clutch pedal, by the time you've lifted said pedal full power is available.

Edited by FP on 03/10/2018 at 18:26

All our cars with Stop Start have restarted instantly, never had an issue.

I'm sure I've read HJ say somewhere that on VAG DSG boxes disabling Stop Start may cause premature clutch failure, for example heavy stop start driving conditions which results in lots of clutch slipping.

So ... coming back to my original question ... assuming that I don't disable Stop-Start, on the occasions when it activates while stopped in traffic - whether the engine is hot or cold - does this indicate that the system is sufficiently "intelligent" to recognise that the DPF is not in the middle of a regeneration cycle?

If so, why disable S/S, doesn't it act as a safety indicator to signal that it is safe to turn off the engine?

...............

In principle I like the idea of engines being switched off while vehicles are stationary in traffic ( I live adjacent to a roundabout on a busy urban A road and am conscious of traffic fumes!), so have no problem with manufacturers fitting S/S and making it the default setting on turning on ignition.

My 3.5 year old Focus 1.5 TDCi stops every time the car stops. The engine is never running when the car is stationary. I like this. However, there is a railway crossing 3 minutes from my house which I go through every day. Clearly the car hasn't warmed up by then, but the stop/start kicks in. If it didn't I'd switch of the engine anyway. I'm I wrong on doing this?

90% of an engines wear is done when it is cold. More fuel is used when it is cold. Keeping the engine running when cold and stationary makes me cringe. Should I mend my ways?

I've just thought - I have no idea when my DPF is regenerating. As I do a high mileage on fast A roads, I'm assuming the DPF is working the way it was designed.