With political uncertainty in oil-producing states, and the rising gas prices that brings, you can expect to see a lot more headlines saying "40 MPG!"

We just did a quick overnight road test of a 2011 Chevrolet Cruze Eco with the six-speed manual transmission, which the EPA rates at 28 mpg city and a stunning 42 mpg on the highway cycle.

Did it get us 42 mpg? No, of course it didn't.

Highway rating vs. real world

You're most likely to approximate the EPA's highway mileage rating if you are driving at the speed limit (or lower) on a nice, flat piece of well-paved highway with no head winds, the windows fully raised, and none of the car's accessories running.

2011 Chevrolet Cruze Eco, New York City, March 2011

2011 Chevrolet Cruze Eco, New York City, March 2011

That, unfortunately, is rarely a realistic situation for how we all drive these days.

Chevy cheats a little, providing an "instantaneous mileage" display in the cluster. It flickers from 14 mpg (acceleration up a hill at speed) to 99 mpg, the most it will register, when the engine is doing essentially no work. The figure is diverting, but also distracting.

Cumulative mileage: 34.4 mpg

The more important number is the cumulative gas mileage. Our results: On a 275-mile overnight journey, in temperatures from 20 to 50 degrees F, we averaged 34.4 miles per gallon.

That's actually slightly better than the EPA's combined 33-mpg figure for the six-speed Cruze Eco. The highway-heavy mix of travel (we only spent perhaps one-fifth of our miles on around-town and low-speed stop-and-go driving) probably accounted for that.

Looking only at highway mileage, it's possible to average as much as 44 mpg for long trips with no stopping and starting. Again, though, very few people spend all their miles on Interstates, much less uncrowded Interstates where traffic flows freely and no one ever has to jam on the brakes.

33 vs 40 mpg? Don't obsess

2011 Chevrolet Cruze Eco, New York City, March 2011

2011 Chevrolet Cruze Eco, New York City, March 2011

Just for perspective, the difference in gasoline consumption between 33 mpg and 40 mpg is half a gallon every 100 miles--or less than $2 at current gasoline prices. If you drive 10,000 miles a year, that's less than $200, or about $4 a week.

While we wouldn't advise you how to manage your money, we think that for all practical purposes, 33 miles per gallon is a perfectly respectable fuel efficiency rating.

$19,745 out the door

The 2011 Cruze Eco we tested had a sticker price of $19,745. That's a base price of $18,175, plus a $525 connectivity and cruise-control package, $325 for the very dashing Crystal Red Metallic Tintcoat paint, and a mandatory $720 delivery charge.

By comparison, the 2011 Toyota Prius--a midsize hatchback, not a compact sedan, with a combined 50-mpg rating--has a base price of $23,810 including shipping.

40 is the new 30

The 2011 Hyundai Elantra, which the EPA rates at 40 miles per gallon on its highway cycle, is leading Hyundai to challenge other carmakers to report how many vehicles they sell rated at 40 mpg or better.

Ford has two separate non-hybrid models that get 40 mpg or better on the EPA highway cycle. To be fair, like the Cruze Eco, they're special option packages--the base versions don't quite hit that magic number.

And indeed, 40 seems to be the new 30 (mpg), or the magic number carmakers want to tout in their ads.


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