Two 2007 RX400h's, two different drivers, two different driving styles--both of ours get between 22.5 and 23.0 mpg, mostly city driving. But my service writer has the answer: Lexus recommends only name brand fuel, never discounted brands like Costco, and claims I can improve my mileage 2-3 mpg. Yuk, yuk, yuk, yuk.
Tom