Vehicle engines seem to turn themselves off automatically when you get out. I have tested this with another player, and it only happens to your client. Everyone else still hears and sees that the vehicle is turned on. It could be dangerous as it appears that your car is turned off, but others can still drive away with it, if they are able to get in. It also kept sending the automatic /me message that "[Player] has turned their engine off.", while his engine was still on and he was outside his car. Vehicles have no engine start sound. They still have a turn off sound. Test
Loving GTA World so far!