

Every once in a while, an advertising claim comes along that strikes a nerve. It makes you stop and glance up at the TV screen, or flip back to that previous newspaper page to contemplate its meaning. For me, it's usually a hair-loss treatment. However, for most people, it's probably something that impacts their pocket book, and a pretty good example of that in the car business recently has been the claim of "40 mpg!"
Never mind the footnote that the "40" referenced is the EPA's "highway" mpg, rather than the typically lower "city" or, more meaningful, combined mileage. That doesn't really matter. An advertisement bannering any variant of "40 mpg" gets your absolute attention if you've just witnessed $65 on the gas pump when the dispenser clicked.

It's a powerful number -- 40 mpg. Car engineers do sophisticated analysis to figure out how to reach it, and the numerical game often comes down to just getting to the threshold where the number rounds up to 40.
It just so happens that we're practiced at rounding up, too -- in this instance, rounding up six significant examples of this rarified 40-mpg breed to determine if any of them are also cars you'd be happy to own.
The select six we've summoned to our investigation are the Chevrolet Cruze Eco (28/42), Ford Focus SFE (28/40), Honda Civic HF (29/41), Hyundai Elantra (29/40), Mazda3 (28/40), and Volkswagen Jetta TDI (30/42). A diesel, but no hybrids? Unlike the public's uneasiness with battery-aided driving (hybrid sales have been stuck around the 2.5-percent range), diesels are hydrocarbon kissing-cousins to their gasoline brethren. We know them. We're comfortable with them. And we were also curious to see how the Jetta TDI stacks-up against its high-tech gasoline alternatives.
" The question we started this exercise with was, "Is there actually a '40-mpg' car that you'd want to own?" Indeed, there is. "
In search of 40-mpg answers, we drove from our El Segundo nerve center to the high desert north of Los Angeles and two destinations we normally visit for our Car of the Year programs. At the first, we grunted our way through a zillion mind-numbing laps of the Hyundai-Kia Proving Ground's 6.4-mile oval in a sequence of stepped, constant speeds to establish our fleet's steady-state fuel-efficiency.
The next day, each car was repeatedly piloted around our familiar Tehachapi real-world driving loop, a richly informative 27.3-mile mix of small-town stop-sign streets, curvy rural roads, elevation changes, and freeway miles. (Another plus is that it's 80 miles from Los Angeles' super-saturated roadways, which are ever on the brink of cardiac arrest.)
Let me explain the meaning of the results you'll see on the following pages. Each car's average Tehachapi mileage, and fuel cost per mile doing so, are obvious. But we've added a figure to this that represents how depressed this is compared with these lap's theoretical mpg modeled from our constant-speed mileages -- that is, what they'd ideally do were they unimpacted by accelerating, fidgeting with the throttle, hill-climbing, and stopping. If you don't drive, uh, very gingerly, pay attention to this one.