Note, however,that “antiquated powertrain” was not listed among its ills.The Sienna’s V-6 and six-speed automatic have delivered praiseworthy power over the years, lending it class-leading acceleration.Perhaps it was a bit coarse at high rpm and fuel economy could’ve been better, but those were minor grievances. And yet the Toyota minivan enters its swan-song year boasting a new engine. Its displacement is the same, but this aluminum 3.5-liter V-6 shared with the 2017 Toyota Highlander produces 296 horsepower and 263 lb-ft of torque, up from 266 and 245.