Question of the week: Is stop/start damaging my engine?
Fri, 27 Jun 2025
Dear Honest John,
"I have just been sent a link by my friend which suggests that auto stop start is not a very good feature to have as it is 'killing your engine' by killing the battery, cam phaser and starter. Should it be disabled whenever a car is started for a journey?"
- SB
Dear SB,
Stop start systems have been fitted to vehicles for years - in fact the first version to reach production appeared in the Volkswagen Golf Ecomatic in 1994 - and the technology itself has been refined and improved over time.
The systems are also designed to only operate when the engine is in the right conditions, so typically they will not operate when the engine is too cold or too hot, which could increase wear. Also the majority of vehicles equipped with stop start are specified with batteries specifically to deal with the increased load.
More recently, mild hybrid vehicles use an integrated starter motor generator (ISG) which has the dual roles of providing extra power to the engine as well as automatically restarting the engine.
However, it is reasonable to say that stop start systems will generate more wear on components such as the starter motor and the crankshaft main bearings. For a fraction of a second the crankshaft will rotate within the bearings without oil when it is started, so a stop start engine will experience this wear more often than one without. As with any engine, good maintenance, particularly regular oil changes are a key factor in minimising engine wear.
It is not true to say it is 'killing your engine', but if you intend to keep your car for many years you may wish to be selective about when the system is functioning.
