Damage to engine? Engines equipped with auto start stop features have upgraded starters to handle repeated uses. Vehicles equipped with auto start stop feature use the starter statistically 12 times more. Battery and alternator are upgraded for handle the extra power consumption from repeated engine starts. Bearing in crankcase on crank and rods are upgraded to a highly scratch resistive material to handle the extra abuse. An engine that isnt constantly running cannot pump oil to bearings when the engine is stopped hence the upgrade to the high scratch resistive material. Even if you permanently disable this feature. It's a good idea to purchase vehicles with this feature available as the engine upgrades are always a welcome in terms of durability.For me the negligible gain in mpg isn't worth the damage it does to the engine.