June 11, 2012
Kim Reynolds - Photos Brian Vance
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.
Testing the Car's Mileage -- and Our Patience
Measuring things like 0-60-mph times and panic stops is old hat for us. But discerning fuel mileage, that's another issue. At a cruise-controlled 60 mph, one of our cars, the Chevrolet Cruze Eco, returned 49.4 mpg. That's 0.0202 gallon per mile, or, if you were to picture that gasoline as a series of teaspoons, one burned every 4 seconds.
A Nissan GT-R can accelerate from 0 to 238 feet in 4 seconds; 238 feet I can measure. But teaspoons of gasoline? Being combusted deep within a densely packed engine? Measure this?
We've all historically computed our mileage just by filling the tank and dividing the miles driven by the gallons added. Nothing wrong with that (particularly if you correct for odometer error). But it's a slow-motion process, and when you're dealing with high-mileage cars (the Jetta TDI, for instance, has a whopping 600-mile highway driving range), it's frame-by-frame slow.
There are far more efficient data-collecting tactics for this, the best being to directly install fuel-flow meters into the fuel lines. However, for myriad reasons -- including our inside-baseball realities that test cars like ours arrive shortly before we test them and the manufacturers don't look kindly on their cars' fuel systems being tampered with -- we've avoided meters (for this round-up). Yet, there remain other good crowbars in our mileage-measuring toolbox.
To produce power, an engine obviously consumes two things: air and fuel. And at constant speeds, their ratio is predictable: 14.7 to 1 -- known as the stoichiometric ratio. It's their perfect proportion for efficient combustion, and when a car's at a steady speed under moderate load, its oxygen sensors are beavering away to keep it so.
We monitored the cars mass airflow sensors (excepting the Elantra's, which employs a different strategy), and, as long as the car is in this steady mode, knowing the air passing through the engine points directly to its fuel consumption. This is what was displayed in a filtered, averaged way on our cars' instrument panels. As a check of this information, we simultaneously logged the cars' slow decline in fuel tank level, and, after calibrating the fuel tanks (incrementally measuring their level versus gallons added), their constant-speed fuel consumption data could be backed up.
Divergence
Our driver's mileage did vary. You hear all the time that you shouldn't expect your driving to duplicate the EPA's super-scientifically derived mileage numbers. Well, before we started our Tehachapi lapping, our drivers were firmly directed to observe the posted speed limits, which inadvertently put our own mileage reproducibility to the test. And the results were actually more divergent than I expected. Below, we list numbers -- and name names.
Oddities? Our differing driving habits had nearly 10 times the influence on the Elantra's mileage than on that of the Focus. Perhaps the Hyundai's more susceptible to enthusiastic outbursts? Mr. Martinez' idea of sticking to the speed limit was taken as more of a suggestion.
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Driver Cruze Focus Civic Elantra Mazda3 Jetta
Evans 43.10 38.60 39.90 38.00 39.40 42.10
Kiino 40.90 37.70 39.90 39.10 42.00 43.00
Lassa 41.70 38.10 41.00 36.70 37.90 41.20
Martinez 35.80 37.70 37.80 31.30 34.10 39.80
Average 40.40 38.00 39.70 36.20 38.40 41.60
Std. Dev 2.7 .3 1.2 3.1 2.9 1.2
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Under Pressure
Every time gas prices spike, the AAA and the EPA nag us to check our tire pressures. After our 40-mpg test-o-rama was complete, I did a little experiment with our long-term Civic Si (the performance-opposite to our test HF). At a cruise-controlled 60 mph, with the tires set to the door sticker numbers, the Civic returned 38.42 mpg. After stopping and immediately lowering them by 5 psi, the mileage (deduced from the mass airflow sensor) declined to 38.18 mpg, or 0.6 percent. Car engineers would kill their dear old moms for 0.6 percent. And all from a little squirt of compressed air.
AutoEnginuity
To raise our data-gathering game we've reached out to Jay Horak and his OBD2 scan tool company, AutoEnginuity, which has become a leader in its field. Don't know what OBD2 is? Feel around under your dash, and you'll discover a hexagonal-shaped receptacle that technicians use to diagnose troubles and check your car's emission system. We're employing it to log speed, rpm, mass airflow, and fuel-tank level -- and, in the case of the Jetta, its diesel consumption in gallons per hour. Cool.
An Anomaly
To measure the cars' speeds accurately, we've turned to our longtime GPS pals, Vbox USA (aka Racelogic). Their data loggers have become the industry standard for GPS-data recording, and they've brought along additional units to supplement those we use for our regular performance testing. A curiosity we've noted is that all the test cars (save the Jetta) are actually traveling slightly faster than their speedometers indicate. Our best explanation is their new (unworn) tires.
'Theoretical mileage?'
We applied each car's various constant-speed mpg results -- acquired under near-perfect circumstances at the proving ground -- to every portion of our Tehachapi Loop having the same corresponding speed to calculate each car's absolutely ideal loop mileage. The difference tells us how real world roads -- and driving -- impacts those constant-speed curves.
Theoretical mileage: 47.4 mpg
Actual mileage: 36.2 mpg
Percent lower: 24
Fuel cost/mile: 10.5c
In the writeups of the following cars, I'll first examine the special technicalities that make them their model's high-mpg iteration. But I can't here because the Elantra we tested is mechanically just like any other Elantra. There's no secret-sauce/high-mpg version because they don't offer a low-mpg version. Indeed, the inscrutable ease with which Hyundai's engines are delivering impressive mileage has some of their competitors genuinely scratching their heads.
Meanwhile, we're scratching ours as to why this example didn't fare better amid this six-car crowd. Exactly a year ago, an Elantra, not unlike this one, accepted the bouquet for beating out many of the same competitors (in their standard-mpg trim). To quote Rory Jurnecka at the time: "Compared with every other car here, the Elantra feels grown-up: the most compelling compromise of styling, packaging, value, efficiency, and comfort." This time? Todd Lassa: "It's electrically assisted steering feels imprecise at low speeds, requiring many tiny corrections; it's numb at higher speeds." Markus echoed this: "The Elantra's steering demands too much attention to maintain a straight-ahead path on the freeway." Notably, it has the quickest steering ratio of the bunch.
Perhaps the initial luster of the Elantra's expensive interior, resplendent features, flamboyant styling, and excellent ride quality has dimmed slightly, leaving us more starkly aware of its functional realities. Markus again: "This mainstream Elantra is devoid of any fuel-economy maximizing coaches; there's just the Active Eco button. And pressing it clearly makes the throttle less responsive -- as if there's a rubber band between the pedal and throttle butterfly." But even in normal mode, our Elantra was the test's slowest (8.9 seconds to 60 mph), despite a power-to-weight ratio second only to that of the Focus (which matched the Cruze and Jetta for quickest time, at 8.1). Some of our original compliments reappeared though, most of them having to do with that relatively plush ride quality.
And its mileage? The right way to think about this is that the Elantra is sort of like the kid with the lowest score in a CalTech physics exam. Still pretty darn good, in other words.
Theoretical mileage: 47.9 mpg
Actual mileage: 38.0 mpg
Percent lower: 20
Fuel cost/mile: 9.9c
Ford has already gotten the message loud and clear that its twin-(dry)-clutch six-speed automatic transmission has been a technological stubbed toe, producing a brittle shift quality and occasionally incoherent judgments. The future of the automobile resides with its software writers, and in this instance, what's scripting the tranny's actions is a good second draft, but far from best-seller-list prose. Opined Markus, "I wonder if this transmission benefits from all the reprogrammed software tweaks recently released? It still seems to display some of the original bad behavior." And, remarkably, our test car was actually built with the wrong shifter. Markus: "It has a +/- button on it, which is not supposed to be on the SFE; and it's taken 5300 miles before anybody noticed." Maybe Ford should revert to a simple six-speed manual a la the Cruze. (I recently drove the one-speed transmission Focus EV, which really solves the problem.)
Our Focus SFE (Super Fuel Economy, a $495 upgrade from the SE) can only be had with this dual-clutch trans. Like the Cruze Eco's efficiency kit, it includes low-rolling-resistance Continental ContiTouringContact tires on aero-covered wheels, speed- and temperature-sensitive grille shutters, and a rear spoiler. The upshot is 2 more highway mpg, which squeaks the car into the 40-mpg game. The average of our conservatively driven, city/rural/highway Tehachapi looping was a respectable 36.7 mpg, 1.3 mpg ahead of the last-place Elantra (with no mpg-improvement package at all).
However, this Focus' absence of cruise control gave us fits during our constant-speed proving-ground lapping (steady-foot Kong drew the short straw), and it didn't make much sense to the other drivers either.
Don't mistake the Focus for a punching bag. Its handling around the figure-eight course was a hoot (only the Jetta and Mazda3 compared), its build quality impressed (shifter notwithstanding), it was quieter than the Cruze, and it has very attractive, multi-color screen graphics (unlike the Chevy's 1980s mono-green look that resembles an old Wang computer). It's a shame to let the transmission distract from all this.
Theoretical mileage: 53.0 mpg
Actual mileage: 39.7 mpg
Percent lower: 25
Fuel cost/mile: 9.5c
You have to wonder if, before our testing began, our cars might have had a brief conversation in the Fairfield Hotel parking lot: "So," starts off the Civic HF, breaking the ice, "this is your first high-mileage rodeo, huh? Well, relax, kids, I've been doing these things for years. You'll be just fine."
Iterations of the Civic HF have been around so long that it's a quasi-cult car now. Even when gas was cheap, there were guys who'd corner you at parties and talk your ear off about how their HF, with cardboard spats taped over their rear wheel housings, once got 67 mpg on a midnight drive down the Extraterrestrial Highway. Under a full moon. The irony is that, with this whole 40-mpg mania suddenly becoming mainstream, the reintroduced 2012 edition of the HF we sampled has gone...subtle.
What makes this HF an HF are two things: aerodynamic tweaks (a small rear spoiler, twin underbody fairings, and streamlined 15-inch aluminum wheels) plus lower-rolling-resistance tires (by 21 percent, in this case). In the HF tradition, simple things go a long way.
However, a Civic tradition we'd prefer the HF dispense with is elevated cabin noise, the main culprit being those tires. Scott Evans: "Any pebble kicked up against the bottom of the car is heard loud and clear. Wind noise is pretty bad on the freeway." Markus: "These tires seem way louder." Kiino: "Too much noise." Honda, are you listening?
Despite the racket, the Civic HF paraded its mileage-making pedigree throughout our Tehachapi laps, a close second to the manual-trans Cruze and better than the Jetta in "energy consumption," if you account for diesel's higher energy content. The HF was behind the Cruze during our steady-speed lapping, something we'd ascribe to the Honda's lacking the Cruze's tall top gear (or any sixth gear). Conversely, the Honda's very tall first five gears may have paid off in our real-world looping. So why is it in 4th place? The B-word: boring. Seabaugh: "The Civic's electrically assisted steering has next to no feel and too little effort. Combined with the underpowered engine, a missing sixth gear, interior noise, and the plastic-fantastic cabin, the HF was a lackluster driving experience." HFs of old were often eccentric, but never, ever boring.
Theoretical mileage: 52.4 mpg
Actual mileage: 41.6 mpg
Percent lower: 21
Fuel cost/mile: 9.8c
In 1905, Swiss engineer Alfred Buchi not only patented a pinwheel-like contraption called a turbocharger, but he knew exactly what he wanted to do with it: attach it to a Rudolph Diesel engine. The German's dizzyingly high-compression cycle produced herculean low-rpm torque, but as the revs rose, the engine's impressiveness declined. And that's where the turbocharger comes in: Whenever extra power is needed, the compressor just bellows in the necessary air. Much of the energy to do it is scavenged from the exhaust heat. Unfortunately, Mr. Buchi was ahead of his time.
By about 107 years -- at least far as the United States is concerned. When future automotive historians conclude when the diesel-powered car finally took off in the New World, they'll point straight at this car: the Volkswagen Jetta TDI. If you drove a diesel back in their bad old days, the Jetta is a revelation. From dead-cold, it takes just a few seconds to fire up; combustion clatter is nearly indiscernible; and the car's hearty torque imparts a sense of being briefly sucked forward, even at highway speeds.
As you can see, its fuel efficiency lives up to its reputation, and impressively, it stays that way even when you put the stick to it. However, here I need to temper all this enthusiasm with an inconvenient interlude of arithmetic.
Diesel fuel inherently packs about 10 percent more energy into each of its gallons, so you need to lower the TDI's mpg by 10 percent for a fair mpg comparison with its gas alternatives. On the other hand, diesel #2 is now costing about 8 percent more than regular grade gasoline (i.e., you're still slightly ahead of the game). But if we compute the Jetta's fuel cost per mile, the Volkswagen's actually beaten (though only slightly) by the Civic and Cruze. Worse, the TDI's base price is over $2000 dearer than those two. If these high-tech gasoline-powered cars are a headache for cost-penalized hybrids, the same goes for diesels.
Fortunately, there are other noticeable benefits to cohabitating with the Jetta. Its light and happy handling recalls that of early 3 Series BMWs, and its looks are attractively conservative (to some eyes) in a category recently gone bodywork-wild. Non-trivial points, these.
Theoretical mileage: 58.1 mpg
Actual mileage: 40.4 mpg
Percent lower: 30
Fuel cost/mile: 9.4c
What if GM took all those great, efficiency-enhancing insights they learned while developing the Volt and applied them to a conventional gasoline-powered sedan? Actually, that's just about what the Cruze Eco is. It's no secret the two cars share platforms, but nothing trains the mind on efficiency quite like creating a car that depends on a battery (at least sometimes), and many of the Volt's teensy and seemingly improbable efficiencies have reappeared on its much better-selling gasoline-only alter ego.
For instance, the Eco shares the Volt's lightweight 17-inch wheels and low-rolling-resistance Goodyear Assurance Fuel Max tires, and deletes its rear-suspension's weight-adding Watts linkage. At times, the weight-savings gets almost fanatical -- the front anti-roll bar's drop links are mainly plastic and whittled with gram-reducing cavities. The fuel tank has contracted by 3.0 gallons to save about 19 pounds (an "exclusive" feature of the manual-transmission version).
Like the Elantra, its spare tire has been replaced with a can of fix-a-flat (only the Jetta actually carries a full-size spare tire; the others are minis). All told, the Eco has skinnied down by 179 pounds compared with a Cruze LTZ RS automatic we tested last year. And where weight has been added, it was for aerodynamic return: The upper grille is more aggressively shrouded, the lower one is sealed at highway speeds, and below the car are strategically placed, air-smoothing fairings. All this was on display on the proving ground, where the Cruze (with its super-tall, Eco-labeled sixth gear) posted far and away the best mileage numbers. Which might make you wonder why it isn't the clear-cut winner here.
We wanted to drive the manual transmission version precisely because of its no-compromise 28/42 mileage. But the actual heads-up match against the rest of this competitive set is the automatic version, and its 26/39 city/highway numbers are a clear step below the stickshift's. And while the engine's torque exceeded our driver's expectations, the shifter itself is so-so (ditto the clutch take-up, which caused me to stall it several times in stop-and-go traffic, despite the car having the shortest first gear). Think of the Cruze Eco manual as the almost no-compromise mileage-maker. Almost.
Theoretical mileage: 50.9 mpg
Actual mileage: 38.4 mpg
Percent lower: 25
Fuel cost/mile: 9.9c
Cars with day-glo "Eco" or "mpg'"badges slapped on their fenders are as often as not automotive empty suits: little more than a tall top gear ratio sitting on a set of skinny tires.
But in the case of the Mazda3's Skyactiv engine technology, this couldn't be farther from the truth. Its 2.0-liter inline-4 is a state-of-the-argument case for advanced-technology gasoline engines, a Bach fugue of interweaving smart ideas with its engineering keystone being an eyebrow-raising 12.0:1 compression ratio. High compression ratios like this are good for efficiency, but bad for knock.
To make it work, the Mazda3's compressed intake charge is cooled by 3000psi, six-hole, direct fuel injection. The next heat countermeasure is that the ensuing combustion is contained by a small cavity at its top to the piston, and finally, long exhaust headers help prevent exhaust heat back-washing into other cylinders. As a kicker, friction has been reduced by 30 percent. Mazda has done its homework, and it showed on the road as the '3 returned better mileage than the both the Elantra and Focus.
That said, it was also the car that most caused us to glance around the room during our deliberations and silently concur that it was the one we could most enjoy driving every day. Let's listen in on the conversation: Evans: "Great-handling car, very tossable with quick steering and very good feedback. The Mazda3 is easily the most fun vehicle to drive at the Proving Ground. Digging the big seat bolsters." Martinez: "A few hundred feet into the heart of downtown Tehachapi, I could already tell it was a solid car."
Naturally, there were a few dings, too: Evans: "The transmission is a bit stingy with downshifts, and that navigation screen is just too small to be so high up and far away on the dash." But Markus summed it up perfectly: "Bottom line, this car's a sacrifice that drives like a splurge."
The question we started with was "Is there actually a '40-mpg' car that you'd want to own?" Indeed, there is -- the Mazda3.
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