By most standards, Lexus’s luxury SUV hybrid has been a smash success since its introduction in 2005. A significant number of Lexus SUV buyers opted for the “hybrid upgrade,” making the Lexus RX 400h, as it was previously known, the most popular hybrid SUV for most of 2009, and all of 2010. The model is now called the RX 450h.

What’s the significance of the shift in the vehicle’s name-number from 400h to 450h? In the gas-powered versions, the number is a code for the engine displacement—so the RX 350 means the vehicle carries a 3.5-liter engine. Lexus nudges those numbers up on the hybrids, because RX 450h’s combination of a 3.5-liter V6 engine and rear-mounted electric motor-generator gives it the performance of a 4.5-liter engine.

Combined, this larger powerplant produces 295 horsepower—27 horses more than did the RX 400h. But despite the added power and the fact that the vehicle is slightly larger than its predecessor, the 450h actually nets 5 mpg more in fuel economy—delivering 32/28 for the FWD version, and 30/28 for 4WD. That makes it the most fuel-efficient all-wheel drive SUV on the North American market.

Base MSRP: $43,935
MPG: 32 city / 28 highway FWD