Used 2012 Mazda 3 Sedan

We're supposed to be pedaling our way to 40 mpg in the 2012 Mazda 3. But we've just turned onto Big Tujunga Canyon, a great road that feeds into the famed Angeles Crest Highway, and it's empty. We floor the throttle without remorse.

Fun driving ruins fuel economy. That's the ugly truth car guys confront every day.

As tougher fuel-efficiency standards loom, Mazda is dealing with it, too. The current-generation Mazda 3 can attack a corner like no other economy car, but it has always had a comparatively big thirst for fuel. The most efficient 2011 Mazda 3 was rated just at 25 city/33 highway mpg.

For 2012, the automaker has added a third engine to the Mazda 3 family — a direct-injected, 2.0-liter inline four-cylinder called Skyactiv-G — and it brings a pair of all-new transmissions with it. Fuel mileage climbs as high as 28 city/40 highway. And when we glance at the average mpg meter after our run through the canyon, it's still not that scary.

Half the Sky
A Mazda official tells us that Skyactiv is a marketing guy's translation of Nobi nobi, which means something like the "sky's the limit" in Japanese. That might not be entirely true, but it's a good story and it gets to the heart of what the Skyactiv technologies are about: They're everything.

Last month, we drove a prototype of the Mazda CX-5 crossover, which will be the first top-to-bottom Skyactiv vehicle, incorporating an all-new lightweight body and chassis along with the new drivetrains. The idea is to build lighter, more efficient cars that get better mpg, yet are still fun to drive — exactly what you'd hope the enabler of Zoom Zoom would be doing.

The Mazda 3 is still a few years away from a full redesign, so the automaker has swapped in only the Skyactiv drivetrains for this 2012 refresh, which also incorporates minor changes to the suspension and unit-body that provide a slight increase in rigidity, along with subtle cosmetic changes.

Rated for 155 horsepower at 6,000 rpm and 148 pound-feet of torque at 4,100 rpm, the new 2.0-liter engine is standard on the i Touring model, which is now available as a sedan or hatchback, and on the new i Grand Touring model.

Mazda is still offering its older, port-injected, 148-hp 2.0-liter MZR engine as a less expensive alternative on base i and i Sport models, while the 167-hp 2.5-liter MZR engine remains on s models for those of you seeking more torque (it's rated for 166 lb-ft at 4,000 rpm). The 263-hp Mazdaspeed 3 carries over unchanged.

Sweated Details
High compression is the key to the Skyactiv-G engine's combination of usable performance and excellent fuel economy. Until now, we'd only sampled European-spec versions of this engine running at 14:1 compression. For the 2012 Mazda 3, the engineers have lowered the compression ratio to 12:1 to accommodate our 87 octane fuel and the 3's more conventional exhaust manifold, which isn't quite as adept as the CX-5's 4-2-1 exhaust manifold at evacuating hot exhaust gases (and thereby preventing detonation).

"The 4-2-1 exhaust manifold is big," Kenichiro Saruwatari, chief engineer for the Mazda 3, told us, "so we cannot package it in the current Mazda 3 chassis — it would touch the dashboard."

Even 12:1 compression would be inconceivable without direct injection cooling the intake charge. A modernized injection system on the Skyactiv-G engine squirts fuel into the combustion chambers at higher pressure than on the automaker's only other D.I. engine — the 2.3-liter turbo on the Mazdaspeed 3.

You'll also note that the new engine is undersquare, with an 83.5mm cylinder-bore diameter and a 91.2mm stroke, compared to the oversquare 2.0-liter MZR engine (87.5mm bore diameter, 83.1mm stroke). Undersquare engines have more compact combustion chambers and suffer less heat loss — Subaru has taken a similar approach on the 2012 Impreza.

Mazda also looked for every way possible to reduce friction on the Skyactiv-G engine. An electronically controlled oil pump is better matched to the engine's lubrication needs, while a new water pump and redesigned fins in the radiator provide more efficient and consistent cooling. The pistons, connecting rods and crankshaft are all forged steel, and the engine has a roller-rocker valvetrain. The engine's variable intake valve timing plays a role in keeping the cylinder contents cool and helps reduce pumping losses in low-load situations.

A Manual for People Who Like Manuals
When we get into our 2012 Mazda 3 i Touring Sedan, we're assured it really is running on 87 octane. Our car has the new six-speed manual, which is Mazda's first totally new manual gearbox since the 1980s.

"Most of the effort went into making the driving experience better," Dave Coleman, Mazda's head of sports car engineering for North America, told us. "Anyone who buys a manual transmission in a Mazda is doing it because they like driving."

To that end, Mazda shortened up the shift throws (now 45mm versus 50mm on the old six-speed) while reducing effort levels. Roller bearings take the place of bronze bushings on the shift rod. There's a nice, positive feel as you slot into each gate, and the clutch take-up is much friendlier than on our long-term Mazdaspeed 3.

With 12:1 compression, the engine has less low-end grunt than we remember from the CX-5 prototypes, but once we reach 3,000 rpm, there's ample torque and it's smooth all the way to the 6,500-rpm redline. It turns out to be plenty of power for the run up Big Tujunga, and we rip off more than a few heel-and-toe downshifts.

Acceleration is just as acceptable on the freeway, and 6th gear isn't so tall that you're constantly downshifting. Fuel mileage is slightly lower with the manual (27/39 on the sedan, 27/38 on the five-door), but not low enough to deter us.

But the Automatic Is Good, Too
If you want an automatic, though, you're not losing out on much performance.

The new six-speed automatic is locked up 88 percent of the time compared with 64 percent on the old five-speed automatic, a change that not only improves responsiveness but also contributes to a 7 percent improvement in fuel economy. The torque converter is only active below 5 mph, so it can be smaller, while the multiplate lockup clutch is much bigger — as is the torsional damper.

Another change is the adoption of a mechatronic module that combines the transmission's electronic and hydraulic controls in a single unit that Mazda calibrates to compensate for minor variations that occur on the production line. The result is a transmission that can rev-match a downshift and still give you a smooth upshift.

That's exactly what we get during an afternoon commute in an automatic 2012 Mazda 3. Downshifts are quick with this transmission, so quick that it's hard to imagine anyone paying more for an automatic-equipped s model with the 2.5-liter engine. Indeed, you'd have a quicker Mazda 3, but it wouldn't shift nearly as well. The automatic has a manual mode (push the shifter forward to downshift, pull back to upshift) but no shift paddles.

Mazda conservatively estimates that an automatic-equipped Mazda 3 with the Skyactiv-G engine will hit 60 mph in 9.6 seconds — significantly quicker than an automatic-equipped car with the 2.0-liter MZR engine (10.3 seconds). A manual-equipped Skyactiv-G car should be even quicker.

It's a Complete Package
Although the drivetrains are the main story on the 2012 Mazda 3, driving this car on back roads reminds us why it remains a favorite of ours in the compact car class.

Even the i Touring trim, with workaday P205/55R16 Bridgestone Turanza EL400 tires, has exceptional grip and balance through corners. Power steering assist remains hydraulic (albeit with an electric motor driving the pump) and the steering feel is beyond what any other automaker has achieved in this price range. Even with only 155 hp, the Mazda 3 is a purer sport compact than some other cars with 50-100 hp more.

The 2012 Mazda 3 is also an excellent value. Our manual-shift i Touring sedan has essentials, including a telescoping steering wheel, Bluetooth and an auxiliary input (a proprietary iPod cable remains a dealer accessory), and costs just $19,245 — right in line with a comparably equipped Chevrolet Cruze, Ford Focus, Honda Civic or Hyundai Elantra. For the hatchback, it runs $19,745, which is $1,000 less than the cheapest 2011 Mazda 3 five-door (which only came with the 2.5-liter). And if you want the automatic, it's $850 more.

Although the 2.0-liter Skyactiv-G will be the volume engine on the 2012 Mazda 3, the automaker isn't expecting an overall increase in Mazda 3 sales, which usually hover around 100,000 units per year.

This is too bad, because the fuel mileage is for real with the new drivetrains, and unlike most other approaches to maximizing mpg, they don't put a damper on the fun. Instead, it's quite the opposite. The Mazda 3 has never been better.

Edmunds attended a manufacturer-sponsored press event to facilitate this report.