The Lexus RX luxury crossover line is the mainstay of Toyota's luxury line in the U.S., representing fully 42 percent of the brand's total 2011 sales.

And the hybrid Lexus RX 450h model finds many buyers among progressive, affluent suburban families.

There's just one problem: Its real-world gas mileage doesn't appear to match its EPA ratings.

Reader Jay Fink wrote last month to Green Car Reports:

I would love to express my disappointment in the fuel economy of my 2012 Lexus RX450 Hybrid. I'm not getting anywhere near what Lexus claims the vehicle should get.

I'm a conservative driver and use premium fuel. Lexus dealer blew me off when I brought this up. Clearly I'm not the only one not so happy.

He's not the first person who's mentioned this, so we decided to check for ourselves.

Over 750 miles: 26.8 mpg

We obtained an all-but-brand-new 2013 Lexus RX 450h from the maker, and embarked on a 750-mile, five-day road test, covering about three-quarters highway and rural two-lane roads.

We obtained an overall figure of 26.8 miles per gallon, according to the car's trip computer.

That's about 10 percent lower than our all-wheel drive RX 450h's EPA combined rating of 29 mpg (30 mpg city, 28 mpg highway).

For reference, the front-wheel drive 2013 RX 450h is rated at 30 mpg combined (32 mpg city, 28 mpg highway).

2013 Lexus RX 450h

2013 Lexus RX 450h

Testing an all-wheel drive 2012 Lexus RX 450h over 1,600 miles to Switzerland from the U.K. and back, we got 31 mpg in stop-and-go urban driving, but only 25 mpg on the highway.

In that case, at least, Lexus warned us that highway travels were not the RX hybrid's forte, and that mileage would be better in the city.

Crowd-sourcing MPG results

But now there's publicly available data to analyze as well. The EPA's website includes a relatively new feature that lets owners of specific vehicles upload the mileage they get in those vehicles.

But for the all-wheel drive 2012 Lexus RX 450h (the 2013 model is too new to have reported data), a grand total of three owners report an average of 29.3 mpg.

For the 2011 model, a single owner reported 20.0 mpg, and for 2010, the average from five owners was 29.7 mpg.

You be the judge

For the front-wheel drive RX models, the 2012 averaged 22.0 mpg (one single owner), the 2011 was 24.0 mpg (one owner), and the 2010 model came in at 24.2 mpg (three owners).

2013 Lexus RX 450h

2013 Lexus RX 450h

None of these figures are validated, and of course it's a self-selected sample and very, very few vehicles indeed. So you can be the judge of its statistical validity.

We would cautiously suggest that the hybrid Lexus RX seems at best to equal its EPA ratings--but in some cases seems to do considerably worse.

23 mpg in Highlander Hybrid

During 130 miles of similarly mixed driving—more freeway miles than urban stop-and-go—we achieved just 23 mpg in a 2012 Toyota Highlander Hybrid, which uses the same basic hybrid running gear as the RX 450h.

The Highland Hybrid, which comes only in all-wheel drive form, is EPA-rated at 28 mpg combined, so the difference is even starker there.

Our test car, moreover, carried a staggering $58,060 sticker price, including mandatory delivery of $875.

The base 2013 RX 450h starts at $47,310, or $8,000 more than the base price of the gasoline RX 350 model.

To that, our lovely Deep Sea Mica metallic blue example added a $5,635 Luxury Package, with leather trim, a one-touch moonroof, folding heated mirrors, a heated wood-and-leather steering wheel, 19-inch alloy wheels, LED headlamps with washers, and a host of appearance niceties like brushed metal sill plates lit by blue LEDs.

On top of that came a navigation system and backup camera, at a stiff $2,775, an $825 Comfort Package of heated and ventilated front seats and rain-sensing wipers, and Intuitive Parking Assist at $500. Wheel locks ($81) and a cargo net ($59) made up the balance of the price.

In the end, we don't have a definitive answer for Mr. Fink.

But unlike the 2012 Toyota Prius liftback--which based on all evidence we've seen delivers gas mileage pretty close to its EPA rating of 50 mpg--we have to caution potential buyers of the Lexus (and Toyota) hybrid crossovers that their mileage may vary significantly from the EPA numbers.

We welcome comments from readers who own or have experience with the Lexus RX hybrid line.

What kind of mileage have you gotten? Is this a car you would consider? Or is the hybrid aspect not necessarily worth the extra cash?

Leave us your thoughts in the Comments below.


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