Consumer Reports got 16mpg in their City Loop with the HH,and 28 hHghway loop.Their city loop must be pretty rugged with lots of traffic lights, lots of stop and go, lots of little trips with a cold engine.Most "normal/average" drivers will get about 10-25% better than CR in the city,and about dead on for the Highway Loop when they are on the interstate at 65mph or so.
Folks on this forum aren't "normal" drivers by any stretch of the imagination.They drive to get good to great mpg using many of the "tricks"-especially P&G(which can be done real world without pissing off your fellow drivers),and driving very,very SLOWLY-which can be a problem.
A normal driver will get about 14-15 mpg in heavy city driving with a V-6 Highlander or a 330 lex.They will get about 25 mpg in pure trip driving.Are you beating those numbers by about 3-4 mpg? If so you are getting about what the average driver will get.If you live in a suburb or city,and mainly drive there you should get about 20 mpg or so with your Lex hybrid.Lotta Hy driving-say a trip-expect about 26-28mpg on the interstate.
My guess is you are getting very low 20's and are pissed because you expected closer to the 30mpg of the old EPA sticker(I think the EPA #s have been changed).
The Prius set an awfully high mark-.26 drag coe and not an awful lot of frontal area to begin with,tiny motor,2900 lbs.You get about 1/2 the numbers that a Prius gets-but most SUVs get about 1/3-1/4 the MPG of a Prius.
Luck,
Charlie
PS-Our 1998 Suburban gets 13 mpg-the Prius get 42-43 in the same heavy city driving.-Roughly 3.5X despite being about 60% of the weight(5400 vs 2950).Hy is about 49 vs 18.Our Pilot-about the weight of your Lexus-got about 14mpg city,and 21-24mpg hy.These are about what the standard 330 would get(the 330 would get maybe 2mpg more hy).