We all know that there are lots of expenses when a new baby's on the way, including all that gear.  In many cases, secondhand items are a good way to save some $$; however, car seats are not an area where parents should skimp.  Now that doesn't necessarily mean not to use an older sibling's seat, or one from a trusted friend or relative (if you can be 100% sure that the seat was never in an accident, and that it was cared for properly), but no parent should ever accept/buy a car seat from a stranger.  There are many reasons for this:

1. Car seats actually expire.  The average "life expectancy" for a car seat is 5-6 years, with very few going to 8.  This information is often available on the seat itself--on a sticker or sometimes stamped into the plastic mold; sometimes a date of manufacture will be provided, with an advisory in the manual as to how long the seat can be used.  There is no wiggle room or leeway on this date--the plastic in the shell does degrade over time, weakening the seat.  Also, parts can be lost, stickers can come off, and new advancements/requirements for safety do come up in the market.  Now many people, including some sellers of used car seats, will say that car seat expirations are a bunch of baloney.  Some simply don't know better.  "How can a car seat expire??", they'll ask, possibly comparing it to dairy products or something like that.  Please remember that the first priority for a person selling a used car seat is not necessarily going to be the safety of your child, it's more likely to clean out the garage and maybe make some money.  They'll tell you an expired seat is just fine, that it's never been in an accident, that there's nothing wrong with it, that car seat companies only make "seats expire so they can sell more seats."  Who are you going to believe, the engineers who designed and tested the seat, or the person trying to unload a seat that's basically garbage onto a buyer?  It's a simple fact--car seats are not safe to use after the date of expiration.  Of course, this is not a knock on all sellers of car seats, as most are honest.  Some just do not know that they are selling a product that could possibly be dangerous; it's up to buyers to be aware that a used seat is not a good idea.  I have heard from some less-than-scrupulous sellers things like "It's not illegal, so I'll sell it if I want" (and if your state has a proper use clause, it could very well be illegal to use an expired seat).  Please don't assume the worst of the seller, however, as some are just not aware of any problem.  Again, it's the job of the parent to avoid purchasing an unsafe seat.

2. Car seats are not safe to use after they've been in an accident, even a minor one.  With the exception of Britax, every single manufacturer of car seats requires that a car seat that's been in an accident, no matter how minor, must be replaced.  The people who design, manufacture, and test the seats are telling the consumer that the seat is not safe after it's been in a crash.  Again, some people feel they know "better" than these professionals, and think, "Oh, it was just a little accident", or "But he wasn't even in the seat when it crashed" (manufacturers draw no distinction between occupied and unoccupied seats).  Bad enough that some people would continue to use a crashed seat with their own children; some might try to sell one.  Again, some may truly feel the seat is fine; some may just not care.  Do you feel you can 100% trust the seller when they say the seat's "Never been in an accident"?  I know I don't.  I won't put my child's life in someone else's hands that way, and you shouldn't either.

3.  You may not get everything you need when you buy a used seat.  Particularly if it's an older seat, parts may have gone missing over time.  Some of these may not matter much, like cup holders, some may be easily replaced, like a locking clip.  Some, however, may be difficult to obtain replacements for, and be VERY necessary, like the manual (can't really install correctly without it), LATCH belt, etc.  Buying new is the only way to ensure you get everything you're supposed to get.

4. The industry is constantly making improvements that make children safer.  For example, car seats used to only rear-face to 20-22 lbs; now they rear-face to 30-35 lbs; since rear-facing is much safer, having that higher weight limit is an excellent improvement.  People who are using expired hand-me-down seats are missing out on this improvement, to their children's detriment.  Now, most new seats manufactured have a 5 point harness instead of a 3 point, shields are becoming rarer, and many have weight limits that are higher than 40 lbs--all good for kids, but not if no one buys them to use.

**Just remember that it's never safe to use a seat if you don't know its history.  What if someone were pulling car seats out of landfills and selling them at their yard sale (after some cleaning, of course!)?  Unless you can personally vouch for the safety of the seat, don't put your child in it.  There are options for brand new convertible car seats starting at around $40.  You can also contact your local SafeKids chapter for information about local safety checks, or if you are financially unable to provide a safe seat for your child.