Class B sprinters typically get 23 - 24mpg
Class C Sprinter dually gets 15- 17 mpg
Sprinter B is pretty dinky and restricted modifications for conversion companies that have to comply with DOT safety.
My Rialta gets 17 - 21 but it burns GAS (ICK)
so... no free fuel for gassers... (
)
Hate it... it will get a TDI + 5 spd swap if the Vr6 ever dies (unlikely it will die)