Miley Cyrus' New Car -- Benz Over for $127k

Miley Cyrus can go from 0-60 in 5.3 seconds ... without a top on ... and all it cost her was a cool $127,000 ... TMZ has learned.

Cyrus dropped by a Mercedes Benz dealership in Encino, CA last week ... and drove off the lot in a brand new white 2012 SL550 convertible.

Sources close to Miley tell us ... the former Disney star paid for the entire thing up front ... because she can.

The best part ... Miley didn't even turn in her old car ... a bodyguard drove it back to her pad so she could joyride in her new toy.

The lesson -- it's good to be rich.