First announced for the 2017 Highlander crossover, the Sienna also gets a new 3.5-liter V6 engine with D4-S direct and port injection. It also now runs on the lean-burn Atkinson cycle for a further boost in efficiency. These tweaks give the Sienna a power boost to 296 hp-a 30-hp gain-while torque jumps from 245 lb-ft to 263. In addition, the Sienna gets two more speeds in its automatic transmission for a total of eight, which simultaneously improves performance and efficiency.
