All new cars already come with Bluetooth compatibility, which makes it easier to stay connected safely while driving.

But what if even the humble aux port isn’t an option? Many older cars lack this connection and, without Bluetooth and USB, they offer no factory-fitted way to connect to a smartphone.

A woman warns car owners to make sure to keep their Bluetooth turned off. She says this is especially true when taking a car to the auto shop. There’s nothing quite as embarrassing as ...