That used to be my theory, until some dumb son of a bitch broke the window without even trying the unlocked door.
I’m confused on issue. A lot of people are saying their insurance is void if there door isn’t locked. Um, how they going to know the door wasn’t locked? Unless you tell them.
If a thief is car-smart enough to hotwire a car, he/she probably has a slim-jim and knows how to use it. So, locking up is not a major deterrent to having it driven off by an experienced thief. But stupid hoodlums, who are looking to make the quickest buck and aren’t nearly as smart, would probably pass up my car if there was an unlocked one nearby. I’d rather not be the nearby unlocked car.
Also, I have comprehensive insurance which covers broken glass (at 100% I think), but as I’m a renter and don’t have homeowner’s insurance, the items *inside *my car are not insured. So it’s more economical for me to lock up.
Different people who are inclined to steal either your car or its contents are going to be dissuaded by different levels of security. Some will smash a window or jimmy the lock; others will try the handles to see if the doors are unlocked and if not, give up.
Locking your doors will keep the latter group out of your car.
Best thing to do about the window-smashing crowd is simply not leave any valuables in plain sight inside your car.
I got a crime alert email from my city the other day that there had been a number (~20) of larcenies out of cars in a couple of neighborhoods over the past two weeks. All of the cars were unlocked.
If my car isn’t in my garage, then it is locked. I also don’t leave anything valuable looking in view.
exactly what my LEO friends say: car theft is almost always a crime of opportunity. in almost all cases, locked doors are the single best deterrent for cars AND homes. aside from insurance company concerns, why would you ever not lock your doors in the first place?
in addition, they say try to keep from having tempting objects out in plain view to any passersby, like an ipod or a cellphone, etc. lying on a seat. when i plan to go into the big bad city of indianapolis for the day, i generally hide my CDs so they can’t be seen.
I used to think that locking the car doors was pointless, when it was parked behind my house, next to the garage, out of sight from the road.
Then someone broke into my car and stole my spare change (which I kept in the ash tray) and my air freshener, which I had not yet opened. My husband’s vehicle was also opened (neither of us locked up then) and they stole his spare change, and coupons to the car wash.
Now, by god, I lock my doors. Crazy people out there stealing spare change and air fresheners!
I read the police blotter for my town, when there are thefts from cars 90% are from unlocked cars. No thanks, I’ll lock my car.
These two statements don’t line up. If the thieves don’t check, then it sure doesn’t hurt to lock the door. As long as there is at least one thief or joy rider who will check, it serves a positiive purpose.
And where in the policy does it say there is no coverage for unlocked doors? I’m not saying an insurance company wouldn’t try to take that position, but they should get their ass sued off if they actually deny coverage for a reason not listed in the policy. They draft those policies and if they want to put that in the policy as a condition of payment, they certainly know how.
How is an insurance company going to prove you left your car unlocked, rather than had it opened by the thief?
Even picking a lock (which is unlikely as hell) leaves telltale damage. If there’s no damage to your lock, door, or windows, it’s obvious that you left the car unlocked.
No-one picks a car lock, they use a slimjim.
Don’t they?
I’m just confused to, if this is a valid reason not to collect on insurance, how the company is finding out. 
If I reported something stolen, which thankfully I’ve never had to, I don’t think I’d start out with “I didn’t lock my car and someone stole it.”
If a car was really gone for good, I just don’t see how anyone (including authorities) would know you didn’t lock the door. I’m not saying you should lie, but in the hussel and bussel of having a car stolen it may slip your mind if you locked it that day. 
So, if your car was stolen, does insurance ask if you locked it?