Is it possible to buy a brand new car with a debit card?

yes you can as long as you credit limit is high enough , and dont for a loan will cost you 10% while a credit card charges 20% 

The mechanism is there, but your bank's rules probably aren't with respect to debit cards. You're free to, you know, make the deal and send them all the money by another method, such as a personal or cashier's check, wire transfer, ACH, etc.

If you have sufficient money in the account and if your bank allows that large of a debit card transaction.

Some dealers impose a maximum limit on card transactions. 

No.

Most dealerships have a maximum amount they will accept on debit/credit cards or they impose a fee above a certain amount.

Most banks also limit the amount you can spend on a debit card in a single day or single transaction.

These limits are usually between $2000 to $5000 which is meant to be large enough to allow normal "large" purchases such as buying a TV or paying for a major car repair or something, but these will prevent you from buying a $20,000+ car on the card.

These limits are there to prevent potential fraud, as well as to limit the cost of the processing fees for card transactions which can be 2-3% in many cases.

Most dealerships will happily work with you to set up a wire transfer, ACH bank draft, or they will accept a personal check - none of which have those limitations.

So yes, you can pay "cash" for a car by just paying for it from the money you have in your account, but no, you cannot do that specifically with a debit card.

Some are saying use a credit card for points/miles:  and if the dealer pays a merchant fee as a percentage of the sale, you'll also pay more for the car!

A debit card is good as cash and usually the merchant doesn't pay a fee . . . . check with your issuer to see if there's a limit on your purchases (even with a big account balance I have a limit on mine in case it's lost or stolen).  And my bank monitors how much and from whom I'm buying - you might want to warn them that a big on is OK.

I have bought many new cars with cash over the years and the debit card is no different.

Be aware that the IRS requires the dealer to submit a 8300 form for any cash purchase over $10,000.

Yes.  They are as good as paper money.

My debit card has a daily limit of $2000. That would mean I'd have to go to the dealership on at least 13 different days to finish paying for a $25,000 car unless the bank is willing to increase the limit on the card to $25,000 or more. Doesn't seem worth the trouble. Have you heard of cheques? They have no limit on the qamount you can write them for. Or email transfers? which might have a limit per transaction.

Yes but they are going to have to report the transaction because it is a cash transaction over $5,000. I hope that your funds can be proven as legal.

i dont see anything wrong with that