The term "sleeper build" is one that we've all heard before. 

While it may have acquired a new meaning in the world of social media, among gearheads 

 refers to a particular automobile that the usual customer "sleeps on" or does not utilise to its full potential.

Sleeper vehicles are typically described as a four-door sedan that looks 

very ordinary yet has a powerful engine. Many vehicles might be appropriate, 

the BMW 5 Series is the gold standard for a sleeper sedan. Every 5 Series since the E28,

arguably, has been a performance vehicle masquerading as an imported luxury vehicle. 

Due to its promotion as a performance car, we would also contend that the M5 is no longer a sleeper