Mileage Challenge 5.2: Avenues and Interstates

Our latest mileage challenge took three hybrids — the Honda Insight, Mercury Milan Hybrid and Toyota Prius — and one diesel, the Volkswagen Jetta TDI, from Chicago to Fond du Lac, Wis., and back. The total distance came to just over 300 miles: The first 38 miles were in urban gridlock, the next 230 miles or so consisted of relatively open highway driving and the final 35 miles took place in afternoon interstate traffic.

As in our other mileage challenges, the ground rules remained largely the same: Four editors filled the tires to their recommended pressure, kept windows and sunroofs closed, drove as we normally would and switched cars at each leg to control for driving habits. But this being a challenge with hybrids there were some added things to look out for that could sway the results.

Three of our contenders had automatic climate control. We set all three at 68 degrees and hit “Auto.” Ford and Toyota told us their air conditioning would run continuously in automatic mode, but both systems use electric air-conditioning compressors that don’t ding gas mileage as much. Conversely, the Insight has a conventional hydraulic compressor, but Honda said it runs on an as-needed basis when you hit “Auto.” That left us with the Jetta TDI, with a manual system that also uses a hydraulic air-conditioning compressor. We scratched our chins, considered our options and settled on leaving the temperature dial at 68 degrees, the fan at half-speed and the air conditioning on. That sounded about right to us.

A further wrinkle: The Prius and Insight both have economy modes that optimize everything from the drivetrain to air conditioning for better gas mileage. (The Prius also has Power, EV and Standard modes; the Insight just has Economy and Standard.) We’d have left both in Standard mode, except the Insight defaults to Economy whenever you restart the car. It stands to reason that most drivers will acquiesce to that, so we did the same — and, to compare apples to apples, we put the Prius in Economy mode, too. (The Milan Hybrid doesn’t have any such programs. It proved refreshingly simple.)

All four cars had trip computers with gas-mileage readouts, which we reset to start each leg. Our varied route gave us a chance to see how each one did, especially given their EPA ratings. The Prius and Milan Hybrid are rated higher in the city, while the Insight and Jetta TDI are rated higher on the highway. Comparing two extremes — 38 miles of urban gridlock during Leg 1, with average speeds around 20 mph, versus 71 miles of interstate driving for Leg 2 at average speeds of 59 mph. Here’s what each car’s trip computer reported:

  • Insight: 52.5 mpg urban, 54.0 mpg highway
  • Milan Hybrid: 45.1 mpg urban, 43.9 mpg highway
  • Prius: 67.0 mpg urban, 60.5 mpg highway
  • Jetta TDI: 38.5 mpg urban, 48.3 mpg highway

The results aren’t too surprising: The Milan Hybrid and Prius did better in the city — the Prius by a wide margin. The Insight did slightly worse in the city, and the Jetta TDI’s split was larger. It also goes to show where each car excels. And on the highway, diesels can keep up with hybrids.

We won’t spill the beans yet, but there’s more to the story. Suffice it to say the fill-ups at day’s end yielded some unexpected results. Stay tuned for more.

Previously: Mileage Drive 5.1: Hybrids vs. Diesel


2010|Mercury|Milan Hybrid





That right! Fill-up! Do you trust that computer?

I do believe this is as I'd predicted it, depending on how much the computers have lied.


Jetta's mileage is a disappointment, considering that next to the Insight it's the smallest car in the test. Also very slow off the line - Prius wins the stoplight derby every time.

Haha, how'd that happen. Brady got the estimates right for the city; I got them right for the highway.

Now wait 'til we find out the Prius didn't really get 65+ MPG lol.

All are still very impressive though. For trip computer readouts.


Not really a prediction when there is so much real-world mileage data out there already to base a "prediction" on.

What is a hydraulic AC compressor? Is that for all the switches? It would be more appropriate to say a mechanically-driven AC compressor.

The computer uses a more consistent algorithm to calculate mileage than the inconsistent fill-er-up method. I track both and the results are usually within +-0.3 mpg.

Billy4202, it looks like the Milan did manage to average out the Jetta overall....


Trip computer readouts are worthless. Only the fill-up will tell the tale.

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