Stop-start: good for the environment—and for the car?

Mandatory stop at a red light: in cars equipped with a stop-start function, the engine automatically switches off. But do you really need this technology? After all, you can easily do this with the ignition key. Moreover: is the continuous switching off and on even worth it? Won’t this overload the engine—resulting in additional costs far exceeding any petrol savings?

Beyond doubt: if the engine is not running while you’re waiting to drive on, fuel consumption is reduced. There is no major difference whether the engine is switched off manually or via the stop-start system. According to ADAC, the saving potential in urban traffic can be up to 15 per cent. This is good news for your purse and also for the environment. Nevertheless, the do-it-yourself method cannot compare with the automatic method.

Stop-start systems know more

For example, if the control unit registers that the catalytic converter is not at operating temperature, the battery is too weak, the vacuum in the brake booster is too low, or the required inner temperature has not been reached, the engine stays on—in favour of safety and comfort. In stop-start systems, factors are consequently analysed, which the driver cannot possibly pay attention to.

Special technology for stop-start systems

Engine components in cars with a stop-start system are designed to take higher loads. Every time the engine stops, the oil pressure drops in the engine’s lubrication system. This can lead to critical micro-friction, which can result in increased wear and thus cause corresponding consequential costs. MAHLE engineers have developed bearings with a polymer coating in which solid lubricants are embedded. This minimises wear and therefore also susceptibility to corrosion as well as premature bearing damage. These bearings are fitted exclusively in vehicles with a stop-start system. Anyone driving a vehicle not equipped with such a system should keep this in mind before switching the engine off at a red light. However, you should obviously switch the engine off during longer waiting times, for example at closed level crossings!

The turbo tip

For turbocharged vehicles, it is advisable after a long drive under a high load to switch off the stop-start system until the exhaust system and the turbocharger have reached a moderate temperature level again.