Quote:
Originally Posted by 42pilot
all the lubricating oil drains from the cam lobes causing increased wear, the oil pressure feeding the main bearings drops to zero and allows metal to metal contact (on every start this happens, and slightly adds to engine wear on each start), allows the engine to heat up further (oil and water cool the internal engine parts) and increases the duty cycles to the starter by a factor of X (for most of us, maybe a factor of 10 at least in medium traffic conditions).
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I think this is a bit over-stated. Yes, there's extra wear, no doubt. But all the engine oil doesn't instantaneosuly drain when the pump stops - it takes several minutes for oil film to dissipate. And since the oil is warm, pressure builds almost immediately when the engine restarts. As for extra wear on the starter motor - sure, but the engine is warm and well oiled (at least compared to a cold start) and the RPMs for restart are very low, so the work required from the starter motor is quite low. Generally electric motors fail due to a combination of age, corrosion, and the stress of having to do heavy work, not so much from duty cycles themselves. I would guess that the wear on the restart is probably 1/10 of cold start wear. You factor X is therefore more like 2 than 10. I owned my last two BMWs for 12 years and 11 years respectively, and never had to replace a starter motor even though they were daily drivers. So the trade off is the potential extra cost of a replacement starter motor that this vehicle may need that it otherwise wouldn't have, versus gas savings.
I will say that it takes getting used to. I find if I don't pay attention at the stop light and suddenly realize that the light has turned green and try to accelerate quickly it's a pain in the butt. The practice I've adopted is watch the lights, and when the cross-street's light turns yellow a slight lift of pressure from the brake pedal - not enough to cause the vehicle to roll forward - is enough to start the motor so that it's ready 3 seconds later when the light turns green. On the other hand my wife hates it and always turns the feature off.