BROOKE SHIELDS tracked down the owner of her first car – a maroon two-door 1983 Mercedes SEC – and decided to buy it back for sentimental reasons.

But to save a few bucks, the former “Suddenly Susan” star, who’s worth an estimated $20 million, got her assistant to negotiate the price without revealing it was for her. That way, the owner had no way to know he was dealing with a super-rich celebrity.

The assistant talked the owner down from his original $7,000 asking price to $5,500 – a tidy $1,500 savings for the penny-pinching performer.

“Brooke got a real steal,” said an insider, adding that similar Mercedes from that year “go for around $10,000.”

The vintage vehicle belonged to Cesar Dural, a 75-year-old retiree from New Jersey who’d bought it from Brooke’s late mom Teri Shields 20 years ago.

The statuesque 48-year-old beauty found out about the car after a fan showed her a for-sale picture of it with a caption saying it was “Previously Owned by Brooke Shields.”

“It was the first car she’d bought with her own money after making ‘Endless Love,’” revealed the insider. “It still had an ‘I love Gstaad’ bumper sticker Brooke stuck on it years ago after vacationing at the Swiss resort.”

Since making the purchase, Brooke had the car painstak­ingly restored and is said to be thrilled to cruise around in it.

“It looks like a million bucks,” said the insider. “And she drives it around Long Island when she and her family stay at their weekend mansion there.”