A Prius makes it easy to measure because it has a mileage computer. My inner nerd was elated at the prospect of getting my own data.
So I kicked back. I coasted and cruised. Above all, I stayed right. Slowpokes in fast lanes are a leading cause of road rage.
I wasn't holding things up. Both highways are often so congested that all I had to do was go with the slower flow.
So to answer the question I got most often: The tally of rear-endings and middle fingers was zero.
But my new leisure allowed me to watch some appalling maneuvers, like the guy in the black sedan that zipped to the right into the exit lane, darted past me and three other cars, then butted back in line.
I also kept closer tabs on my rearview mirror - which one day on the ramp from the Vine Street Expressway to the Schuylkill showed the driver behind me, head resting on the side window, mouth agape, eyes closed and the car moving.
How do you beep at the guy behind you?
Even if people believe going slower will improve mileage, few actually do it.
In a recent survey for Access America, a travel insurance provider, 67 percent of respondents said gas prices changed their driving habits. They reduced recreational driving or consolidated errands. Only 2 percent were lifting the pedal off the metal.
U.S. Rep. Jackie Speier (D., Calif.) thinks it's time for national legislation. This month, she introduced a bill calling for a national maximum speed limit of 60 m.p.h. in urban areas, 65 in rural.
It wouldn't change much in this region, but 12 other states allow speeds up to 75.
We've been down this road before. A year after the 1973 oil crisis, the government capped speeds at 55.
Willie Nelson urged, "Don't be fuelish!" but people still sped. The law was repealed in 1995.
Still, things are different now.
I took to the road with my tires properly inflated and my trunk emptied of excess weight.
A pit crew of supporters shared tips like the "Broad Street coast," floating when the light a block ahead is red.
One brave soul goes 55 on I-295 in Jersey - where the most recent stats show that more than two thirds of drivers exceed the 65-m.p.h. limit in Cherry Hill. He put a sign in his window: 55 mph=36 mpg.
Another driver says that after feeling like a chump - he hated being passed - he's now in "a new emotional state. I kind of gloat. I'm doing the right thing for the environment."
My own mileage bumped up immediately.
I drive the two highways every day, and I could always get 52-55 m.p.g. if I was careful. But still, I was often driving between 60 and 65.
Now, I backed off to between 55 and 60. This required some attention. I'd find myself inching up. I tried cruise control, but it was easier to find another slow driver and follow.
Most surprising, I wasn't anxious about being late. It felt so Zen. Everything slows down anyway at the big Girard Avenue backup.
I've decided I can do this. In fact, I want to stick with it mainly for my sanity.
But the mileage is great, too. My personal best over a stretch of 23 miles into town, with a nice downhill portion, was 68.4 miles a gallon.
Most of my driving is on the highway, so if I could keep this up, I might save a couple hundred dollars a year.
I won't get rich. But does anyone mind if I gloat?
GreenSpace: Get Better Fuel Efficiency
Drive gently. Rapid acceleration and braking can lower mileage by a third.
Reduce weight. Every extra 100 pounds can reduce mileage 2 percent.
Maintain your car. Keep your engine tuned, your tires properly inflated, and your air filter clean.
Avoid idling. That gets you zero miles per gallon!
Commute during off-peak hours.
For more tips and information: go to www.fueleconomy.gov, www.DriveSmarterChallenge.org; www.greenercars.org.
Contact Inquirer staff writer Sandy Bauers at 215-854-5147 or email@example.com. To post a comment, visit her blog at http://go.philly.com/greenspace.
Turn down the A/C. You could open the windows instead, but increased speeds mean increased drag.