Highlander and RX powertrain optionsV6 power left the Toyota Highlander's engine bay with the debut of the 2023 model year, coinciding with the launch of the fifth-generation Lexus RX and its lack of six cylinders. Both models rely on different forms of four-cylinder power. The Highlander Platinum's powerplant options are straightforward. The standard engine is a turbocharged 2.4-liter inline-four making 265 horsepower. It's connected to an eight-speed automatic transmission and is EPA-rated at 24 mpg combined. The Highlander Hybrid uses a naturally aspirated 2.5-liter four-cylinder engine paired with a hybrid system that delivers 243 net horsepower.In typical Toyota fashion, the gearbox is an electronically controlled continuously variable transmission (eCVT). These Highlanders have a combined fuel economy rating of 35 mpg. The RX offers numerous engine choices. The RX 350 shares the Highlander's 2.4-liter base engine and transmission but gains an additional 10 horsepower while still delivering 24 mpg combined. Similarly, the RX 350h piggybacks on the Highlander Hybrid's 2.5-liter unit but ekes out three additional ponies and one extra combined mpg. Output increases significantly with higher RX variants.The 2.5-liter hybrid gets the plug-in treatment in the 450h+, which is good enough for 304 combined horsepower, 37 miles of all-electric driving, and 36 combined mpg. The 500h adds turbocharging and hybrid technology to the 2.4-liter four-cylinder, yielding 366 horsepower and 27 combined mpg. Yet this most powerful RX uses a six-speed automatic instead of the eCVT in the other RX hybrids. All RX information here reflects AWD.