On a couple of occasions recently, I've had to leave the bike locked in the car overnight, once outside my house, and once at my inlaws. Both places are fairly rural, we live on the edge of town down a single-track road that goes into a bridleway, and my inlaws live in the middle of no-where in Wales.
Both times though I've used my Kryptonite D-Lock to secure the bike in the car, using the flex cable hooped through the square steel bracket of the rear seat catch, which is welded to the body of the car. I figured it would be a good thing to get some level of protection to acutally lock the bike to the car, and not just lock it in it.
I hope this helps if anyone does leave their bike in the car regularly, or even occasionally. An extra bit of security could help stop your bike being nicked in a smash and grab as the thieves may not have the tools to get through a security cable.
Both times though I've used my Kryptonite D-Lock to secure the bike in the car, using the flex cable hooped through the square steel bracket of the rear seat catch, which is welded to the body of the car. I figured it would be a good thing to get some level of protection to acutally lock the bike to the car, and not just lock it in it.
I hope this helps if anyone does leave their bike in the car regularly, or even occasionally. An extra bit of security could help stop your bike being nicked in a smash and grab as the thieves may not have the tools to get through a security cable.