After developing a hybrid drive system for its 7-series, it becomes a no-brainer for BMW to extend that technology to its 5-series. Similar to the ActiveHybrid 7, BMW took an existing 5-series model, the 535i, and added the hybrid system. This strategy increases both fuel efficiency and power.
In the combined European Test Cycle (BMW has not conducted EPA fuel economy testing yet), the ActiveHybrid 5 achieves 33.6 mpg. Although far from the 50 mpg of the Toyota Prius, the ActiveHybrid 5's fuel economy is excellent for a car delivering 340 horsepower, and able to get to 62 mph in 5.9 seconds.
Besides the hybrid system, the ActiveHybrid 5 is, in almost every other sense, a typical BMW 5-series. The cabin proportions are the same, although the hybrid system adds significant weight to the car, an extra 360 pounds. Despite the extra weight, the ActiveHybrid 5 turns in 4 mpg better fuel economy than the 535i.
The hybrid system uses a lithium ion battery pack, placed in the trunk, storing 1.35 kilowatt-hours. It feeds a 40 horsepower electric motor, which can drive the car up to 37 mph. BMW also says the electric range is 2.5 miles. The hybrid system gives the car idle-stop capability.
These optional 18-inch alloy wheels are designed for aerodynamic efficiency. The car also has regenerative braking capability, which recharges the battery when the car is decelerating. The car also has a mode called Eco Pro, which completely decouples the engine from the wheels when coasting at speeds under 100 mph.
Along with ActiveHybrid 5 badging on the truck lid, the car carries this nameplate on the rocker panels and on the center console. The instrument cluster also shows hybrid performance, as does a power-flow animation on the center stack display.
The gasoline engine is BMW's tried and true twin-scroll turbo direct injection 3-liter straight six. By itself, it is more than adequate for the 5-series, producing 306 horsepower. But the hybrid system adds both power and fuel economy, efficiency gains that are hard to argue with. In addition, the hybrid system lets the car drive in electric mode, useful for stop-and-go traffic or urban zones that only allow electric vehicle operation.
Along with BMW's excellent suite of cabin electronics, the ActiveHybrid 5 also uses the navigation system determine the best hybrid engine operation for the upcoming terrain. For example, if there is a hill ahead, it might lean more heavily on the gas engine.