I am about 4k in credit card debt and I was ...

jjoan, It's almost always a bad idea to borrow money to pay off a debt.  $4000 isn't that much, but think about this.  You will be buying a car, maybe a good deal right now and get a 3 year loan or longer I'll bet.  You don't have any or much of a down payment on the car so you will have to borrow the full amount.  Very few loan companies will loan more on a car than it's worth so I doubt you can even swing the deal you're talking about.  One exception is if you own property then it could be a good deal.  Anyway, if you can swing it you will then drive the cost of the loan on the car to $4000 more than the car is worth.  You will be what's called up-side-down which means you won't be even on the car till almost the time the loan is paid off.  If the used car goes south before the loan is paid for you will be paying the loan on something you can't even use!  Contact the CC and see if you can negotiate a lower rate of interest.  Try to get the cc's paid off asap then go for the car.

I must say, I totally disagree with Colo Bob.  If it's a bank loan you intend to get (the only way to get more than the car value), borrowing enough to pay both the debt and the car is called "debt consolidation" ...and if the rate is considerably below the rate on your debt and not more than the rate on a dealer car loan, it's a very smart idea that would bring down your monthly debt service cost!  If the car dealer can offer you a better car loan rate than your bank can offer on a personal loan, it would be better to get the dealer loan for the car but still go ahead with the personal loan from the bank to pay off the credit card debt.

jjones,  Of course the point Lin Janson-Will is correct about a bank loan.  But with you owing the small amount, to most of us, on the credit card and wanting to buy a used car I doubt you have the credit available to get an unsecured loan at a bank.  Also unsecured bank loans usually are shorter termed than auto loans which will drive your payment up.  I stick with what I originally said, get a lower rate on your cc bills, either through negotiation, or lower rate of interest from other lender, then buy the car.  You might even look at a new inexpensive auto with no interest for 60 months.

jjones, colo Bob is a smart guy....and he's given some good advice!....but I'm still responding to your statement that the interest on your $4000 debt "is killing you" (I KNOW!...it can be $1000 a year or more)...so just let me add this short anecdote...

As a single Mom raising 2 kids,  I drove 5 or 6,000 dollar cars until 4 years ago...never 16,000 dollar cars, as the difference between your $20,000 loan to include paying off your debt would indicate.  That said, I bought a house on the back of Vail mountain and another in Sedona...wore thriftshop clothes...and paid off the two houses in 7 and 6 years, respectively.  Yes, I lived like a pauper, and my cars were...uhhh...unimpressive?...but now I have two paid-off houses, a new car, no debt, and a $1,500,000+net worth. ....Perhaps you should get a loan (if you can) to get rid of the credit card debt and buy a decent but unimpressive car (deals are out there, these days!) and do what I did.... calculate your monthly expenses, put aside the money before they come due, and spend only that much as you have left after expenses.  It's a real drag for awhile....trust me!....but filet mignon and crab for dinner - no debt - new cars bought by check - pay off in the end!

                The key?  Spend less than you make!

You want to shift your unsecured debt to a secured debt loan. Not a good idea.

A credit card debt is unsecured debt and the credit card company cannot claim anything for non-payment or late payment of debt. Whereas car loan is a secured debt, you could eventually loose your car if you cant pay the loan amount back.

I would not suggest that it is a good idea.

I agree with Thomson here. It would be simply foolish to get a secured debt to pay for an unsecured debt.

Colo Bob's advice is spot on.  If you are finding the (relatively) small debt on your credit cards to be a burden, it would absolutely be a bad idea to start taking out secured loans.  It seems an easy option, it might (in a small amount of cases) mean that you're onto a winner, since you repay over a longer period and typically less of that is interest each month (in terms of ratio... capital repayment vs. interest fees). 

However, without exception it's usually a bad idea to go down this route because people find themselves slipping further and further into debt with no real idea of how they got there or how else they can fix the problem.  Don't go past that line right now - you have a choice whether to step back.  Especially since two things jump out from your question... that you don't really clearly say how you "need" a car... there are different levels of need, if you just don't like the public transport or some trivial matter like that then it's a no brainer, which is what I suspect since you didn't provide any more detail on this "need". And the second thing is your wording - forgive me if I'm reading too much into this - but you're "thinking"... good that you're pondering but again suggests no real desperation.  It's a Want, not a Need - that's what your wording screams to me.

If you want more information on why it's such a bad idea debt consolidation I recently did an article on this very topic on my website, check the link if you want.  But in 90% of cases consolidation is a bad idea, most people go into it without really understanding the implications .  It can be a great option, but not for everyone...