[Zigurd]

Cars have a number of processors, mostly running RTOSs, mostly controlling subsystems, like window motors, seats, etc. It's this way because these subsystems come from different suppliers. A lot of them do not need high stakes security hardening or hard real time capability. These will increasingly get integrated into software modules that can run in an evolved main "infotainment" system.

[slt2021]

small car components are just MCUs, bigger units like ECU are large SoCs with full fledged RTOS like Integrity RTOS (which can be found on everything from cars to F-22 Raptor jet)