A number of features and systems help to enhance fuel economy while still maintaining the performance levels of the previous Impreza 2.5i. A dramatic increase in EPA-estimated fuel mileage was accomplished through improved aerodynamics, light weight, all-new engine, Lineartronic CVT (Continuously Variable Transmission), and chassis improvements.
In order to lower the coefficient of drag (Cd) for the new Impreza, Subaru engineers optimized the structures of both models for lower drag. That’s part of the reason for the sharper appearance of the front and rear; those details contribute to uniform airflow. Here are some of the aerodynamic improvements:
- Smooth areas surrounding the fog lights
- Sharper edges on the rear bumpers
- Small tips at the back of 5-Door roof rails (included on the Sport model) help smooth airflow
- Specially shaped mudguards under the front wheel wells
- A large cover under the front end
- Air flaps in front of all four wheels
As a result, the Cd for the 4-Door dropped significantly from 0.331 to 0.306 and for the 5-Door from 0.343 to 0.329.
In 2.0-liter form as installed in the Impreza, the FB engine is a more fuel efficient version of the 2.5-liter found in the Forester.
The engine is designed with a longer stroke and smaller bore design. As a result, the intake ports are smaller, which induces higher airflow speeds through the ports; the fuel and air mix quicker and more uniformly within the combustion chamber for faster and more efficient burning. Torque at low- and mid-range engine speeds is enhanced. Overall, the engine has cleaner exhaust gas and greater power (per unit of displacement).
Some other components contributing to improved efficiency:
- Tumble generator valves, which create vortices within the combustion chamber for quicker air/fuel mixing
- Intake system with reduced resistance
- Intake and exhaust Active Valve Control System (AVCS) improves power output, fuel efficiency, and exhaust-gas performance
- Exhaust Gas Recirculation (EGR) system that cools the EGR gas for improved fuel efficiency and cleaner emissions
- Low-tension piston rings, lower piston weight and connecting-rod weight, roller rocker arms, and chain-driven valve system – all of which reduce friction
Models with the CVT achieve the highest EPA fuel economy ratings. This is not the same CVT found in the Legacy and Outback. The Impreza CVT is lighter and more compact. Its wide ratio gearing and advanced chain drive improve operating efficiency by 10 percent over the previous four-speed automatic transmission.
Also helping to improve fuel economy are
- Tires specifically designed for the Impreza reduce rolling resistance by 6 percent (helping improve fuel efficiency by 3 percent)
- Spring-type pad returns added to the front brake pads help reduce drag
- A fuel-economy gauge helps drivers see when they’re driving efficiently … and when they’re not!
||2012 Impreza 4-Door
||2012 Impreza 5-Door
||2011 Impreza 2.5i
|Fuel economy (city/highway/ combined)1
||Manual: 25/34/28 mpg
CVT: 27/36/30 mpg
|Manual: 25/34/28 mpg
CVT: 27/36/30 mpg
|Fuel economy (city/highway)2
||Manual: 20/27 mpg
Automatic: 20/26 mpg
1 2012 EPA fuel economy estimates. Actual mileage may vary.
2 2011 EPA fuel economy estimates. Actual mileage may vary.