The only thing I leave in my cars are 5 round HKS speed loaders for the J-frames I habitually carry.

I take the speed loaders out when I have a car serviced! On the rare occasion I must go into a building where I cannot carry I keep my fingers crossed and leave the gun in the car until I get back.

But I would not leave a gun in the car as its permanent location since I have had a couple cars stolen in my time. I got them both back but there was no gun in them for the crooks to keep. Come to think of it, that was back when you could hot wire a car - shows how old I am!