As we've outlined in a previous long-term update, the 2012 BMW 328i's instrumentation combines a digital rendition of their familiar fuel economy "needle" with a twist: When Eco Pro mode is selected, the functionality of the display switches to a setup designed to inspire more fuel-efficient driving. But is it really effective enough to significantly boost your mpgs? We took to the road to find out.

The Setup: Stark Simplicity in the Name of Function

Unlike more graphically complex setups found in cars like the Ford Fusion Hybrid, which incorporates "Efficiency Leaves" that reward mellow driving by growing, BMW's EfficientDynamics interface is simpler and considerably less ornate than the Ford arrangement. When the BMW's Eco Pro mode is selected, the efficiency needle simply changes its color-coding and calibration to discourage swinging the needle too far to the right. But behind the scenes, Eco Pro's inner workings are complex: Not only does the setting work with the "smart" alternator by reducing the air conditioning system's load on the drivetrain, it recognizes pedal behavior and alters the throttle response so fuel economy savings can reach up to a claimed 20 percent.

If you're lead-footed or accelerate past 75 mph in Eco Pro mode, the dash offers a small display message suggesting you lay off the pedal. On the flip side, a mellow right foot rewards you with a display indicating how many miles of range you've gained based on your selection of the neutered mode. At the end of the tank, figures can be as little as the low single digits or as high (theoretically, at least) as BMW's estimate of 20 percent.

From the Driver's Seat

The eco-conscious mode feels noticeably more sluggish than "Normal" or "Sport" modes. Acceleration is considerably slower, which makes it feel like there's a lag between the gas pedal and the engine. While this BMW is one of the more driver-oriented options in the segment, Eco Pro mode erases those feelings of connectedness in favor of outright fuel economy. We're OK with it, since it takes an active choice by the driver to select the mode and can be easily disengaged when the mood arises.

In my experience, it's always fun to flip the switch to "Sport" and drive like the Dickens. But once you've gotten speed out of your system and (hopefully) successfully avoided getting nabbed by law enforcement for your velocity transgressions, there's something relaxing about driving from A to B in no particular hurry. That said, Eco Pro isn't the most thrilling way to cut through city traffic or run down the highway. In fact, it's intrusive enough to annoy impatient drivers with its syrupy slowness. But if you can stand the watered-down driving experience of reduced engine power and responsiveness, you'll be rewarded with instant information indicating how many miles you've gained for your frugal ways.

The Numbers

When equipped with an automatic transmission, the 2012 BMW 328i is rated at 23 mpg city and 33 mpg highway. The 6-speed manual transmission produces a highway rating of 34 mpg. But did those figures translate in the real world? After crunching our fuel economy numbers, our real-world fuel economy hasn't strayed more than 2.5 mpg from the trip computer's numbers. We've hit a high of 29.3 mpg and a low of 23.2 mpg. Our overall average fuel economy was 25.8 mpg, which is not far from the combined Environmental Protection Agency (EPA) estimate of 27 mpg -- pretty good, considering the fact that our low-key driving habits were interspersed with some speedy excursions and a fair amount of city driving.

Real-World Gains

We were initially skeptical about using Eco Pro regularly, as a performance-focused machine like the 328i seemed to beg for aggressive driving. But once the thrill of flogging the 328i started wearing thin, the fuel-saving measure became increasingly tolerable. It ultimately became something we didn't mind using, since it gave us a tangible way to witness our mileage gains for each tank of gas.

Though we never gained more than a dozen or so miles per tank by the mode, that was usually enough to make the effort worthwhile. As the cliche goes, a mile saved is a mile earned. And of course, we never hesitated to switch back to more responsive modes when the mood arose. After all, you can't deny this Bimmer's sporting personality for too long when it's begging to be uncorked.

author photo

Basem Wasef is an automotive journalist, author, and photographer with two coffee table books under his belt, and is a regular contributor to Popular Mechanics, Robb Report, and Maxim among others. When Basem isn't traveling the globe testing vehicles, he enjoys calling Los Angeles home.

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