Is Start & Stop technology good or bad for my car? (Alfa MiTO)

Question

I was recently in the lucky position to obtain an (almost brand new) Alfa Romeo MiTo, Progression. Like many new cars coming out these days, it has "Start & Stop" technology that turns the engine off when the car is stationary and is put in neutral and the clutch is released. When putting down the clutch again the engine fires back up.

My question then is this:

a) Is start-stop technology bad for my engine in any way?

b) What impact might start-stop have on my battery? I.e. won't it deteriorate battery life with the constant turning on and off? (The radio, fans and lights remain on whilst in "stop"-mode, but not things like the aircon.)

c) Will this technology really benefit me that much with regards to fuel-consumption? I can imagine it will be more economic when stops in heavy traffic become really long or traffic lights are red for long periods, but for the most part when driving the car doesn't turn off for longer than a minute at most before I have to "start" it up again.

As many new cars lately have this technology I imagine that it can't be that bad, but I'm curious as to it's actual real benefits. I can turn this feature off, but I have to do so every time I start my car up for the first time and then I'm stuck with this glaring orange light in my dash, letting me know it's turned off.

Answer 1

I would imagine that this sort of technology would lead to increased wear on your starter motor, as it is being used far more than it would normally be, however I would hope that they would have anticipated this and designed the starter to be more robust than a traditional one.

The battery should be able to cope with it fine all the time it is in good condition. Batteries do, however, deteriorate over time, with a usual life of around 8-10 years at most. I suspect that as your battery starts to deteriorate, it won't be able to cope as well with the increased drain, leading to the car failing to re-start with traditional flat-battery symptoms. How well the electronics cope with this remains to be seen!

As to your third question, I doubt it will help much at all. Getting an engine started needs quite a lot of energy (hence the big chunky battery), and the only way to get that energy is to burn fuel, through your alternator sapping power as it recharges the battery. I don't know the exact figures, but I suspect you'd have to have the engine off for a fair while to save enough fuel to offset the cost of starting it again.

Answer 2

Potential savings from reduced idling should greatly outweigh any increased wear and tear on starting and charging systems. I answered similar question about idling before (Is idling bad for your engine?). To summarise the negative effects of idling:

• Fuel combustion is incomplete, which leads to contamination of combustion chamber (glazing), spark plugs (wich reduces their effectiveness), exhaust system (including catalytic converter).
• Motor does not operate at optimal temperature, which leads to excessive condensation of water vapour in exhaust system, which leads to its corrosion (ergo premature replacement), and increased emissions.

At the same time cost of wear and tear is low (American governmental agencies routinely cite $10 added per year). Roughly, it means if one would expect to replace the starter at 10–12 years normally, now one would do it at 8–10 (I pulled these numbers out of me arse, but they seem reasonable).

To quantify fuel savings we need to consider savings from reduced idling, and savings from avoided performance losses. Research paper from Vanderbilt University (Amanda R. Carrico et al, “Costly myths: An analysis of idling beliefs and behavior in personal motor vehicles.”) based on the survey of 1300 U.S. residents estimates that on average Americans spend about 16 minutes a day idling (4 minutes warming, 4 minutes waiting, 8 minutes in traffic). Possibly, in more compact European or South African municipalities these numbers could be lower.

Let us say we cut American number by about 60% and save around 6 minutes a day. 2.0L 4-cylinder petrol engine burns around 1 litre per hour idling. 6 × 365 / 60 = 36.5 hours/year, or 36.5 litres/year.

Reduced efficiency can cost even more. If a car is driven 1500 km (930 miles) a month or 18000 km (11100 miles) a year, and consumes on average 9L/100 km (2.0L compact), 5% reduction in efficiency leads to 0.05 (18000 / 100 × 9) = 81 litres per year extra.

So average Golf-class 2.0L 4-cylinder compact can consume extra ~120 litres (31 U.S. gallons) every year due to excessive idling. Multiply that by the price of petrol, and see potential savings on the fuel alone.

Answer 3

Most modern car manufacturers do proper research, development and testing before they introduce new features in an automobile. Since start and stop technology was not existing some years back, older vehicles will not benefit from this function. Newer cars which already come installed with such features have no problem whatsoever, but it is advisable to shut off this option in extreme bumper to bumper traffic.