While Honda's Insight Hybrid bears a close resemblance to a Toyota Prius, I found the external design of the Honda garnered more attention from passersby, perhaps due to cleaner, less cluttered lines. If the two cars are side by side, the more tapered nose of the Honda and its less tapered rear roofline are readily apparent and may account for the increased attention as a sleek machine rather than the rounded look of a giant mouse (my whacked out impression of the Toyota).

2010 Honda Insight

2010 third-generation Toyota Prius

The cars' shape and size govern aerodynamics and drag. The Honda is just over three inches shorter than the Prius (six inches less in wheelbase), but more importantly 2.5 inches lower and two inches narrower—which means less frontal area for less drag (proportional to drag coefficient (C_D) x frontal area).

But even though my aero engineer's intuition would think the Insight has a lower drag coefficient (essentially dependent on shape and "smoothness"), in fact the Prius C_D is given by Toyota as 0.25, with published Insight numbers ranging from 0.26 to 0.28. Perhaps the differences are due to conditions differing for the measurement of each car, not to mention accuracy.

Now looking at the EPA mileage numbers: The Insight gets 40 mpg (city)/43 mpg (hwy) and the Prius 51 mpg (city)/40 mpg (hwy). These fuel economy results show that obviously more than drag is involved, including engine performance and economy, transmission scheduling, and hybrid systems integration, control, and programming.

When I drove the Insight last week, in just over 120 miles, I logged a bit over 45 mpg in suburban driving. The car had many features to give a driver a sense of how his or her driving style is producing maximum fuel efficiency. These include eco-scoring an individual trip or total accumulated driving and an Eco Drive Bar in the instrument cluster that portrays economical acceleration and maximum regenerative braking.

I found the best indicator was the colored surround lighting of the digital speedometer at the base of the windshield, which is conveniently always in the driver's peripheral vision. This light ranges in color from deep green, to blue-green, and then to deep blue in going from very eco-friendly to more inefficient. (I even became used to using the digital speed readout even though I prefer an "analog" needle display which doesn't have to be "read;" only glanced at for a speed indication.)

There is also an "ECO" button that switches the car into modes maximizing economy at the expense of livelier performance (with also greater climate control fluctuation). For example, a slower acceleration rate when the cruise control is set to resume speed or accelerate.

One small negative was the rear sightline, because of the low sloping hatchback glass, was somewhat restricted, although the vertical rear panel of the hatch is clear for visibility. But the rear window wiper housing also cuts the view out the back, along with the horizontal hatch frame joining the rear window and the vertical rear panel. (This bar did serve as a convenient light shield of headlights on following cars at night!).

Shortcomings in rearward view were made up with large side mirrors—but then again, these add to drag, bring this discussion full circle.