NEW YORK (MainStreet) — Buy car this New Year's Eve and you'll have plenty of reason to pop some champagne. A study has found that Dec. 31 is the absolutely best day of the year for deals.

"What we see on Dec. 31 is the biggest percentage discount of the year off of manufacturer's suggested retail prices," says Larry Dominique of TrueCar, which analyzed millions of 2013 car purchases to see when consumers got the biggest bargains.

TrueCar found that shoppers who bought vehicles on Dec. 31, 2013, paid 8.66% on average below MSRP. That's the highest discount of the year — more than 1.5 percentage points better than the 7.15% off of list price that consumers got on average during 2013 as a whole.

Dominique, a former Nissan executive, says automakers and dealers team up to offer low prices at year's end because everyone wants to close their books with as many sales as possible.

He says manufacturers want to brag in the coming year about who has America's top-selling models, while dealers aim to be No. 1 in their market — and often get bonuses from automakers if they hit annual sales targets.

"Dec. 31 really is that last chance for both the manufacturer and the dealer to make that last sale of the year and maximize their numbers," the expert says. "If they need a few more sales to make a certain number, I guarantee you that they'll practically give cars away."

Dominique adds that dealers and manufacturers also want to finish December strong because wintry January is usually the industry's slowest month.

Jack Nerad of Kelley Blue Book calls year's end "one of the best times to buy a new car. "In the wake of Lexus' highly successful 'December to Remember' campaign that first launched years ago, many automakers have been offering holiday sales events — making now an opportune time for shoppers to get a deal on a car they may have been eyeing all year."

KBB's top picks for December bargains include, in order:

  • A $4,000 rebate on any remaining 2014 Mazda CX-9s. This popular three-row crossover sport utility vehicle lists for $30,815, but KBB says you can get one for around $23,749 after factoring in the cash back.
  • A three-year, $189-a-month lease on the 2015 Chevrolet Malibu midsized sedan, with just $1,369 due at signing.
  • A $1,000 rebate and a zero-percent five-year loan on any leftover 2014 Toyota Avalons. KBB says you should expect to pay about $27,716 for this full-sized sedan after accounting for the rebate.
— By Jerry Kronenberg for MainStreet