Thursday, August 7, 2008

I can't drive 55! Will 60 work?

About a year and a half ago, we bought a Prius. This has turned out to be the single best purchase we've ever made, and that includes the really awesome set of pasta dishes we bought on sale at Sam's Club about 10 years ago for $5 and still use almost every day.

The Prius has an 11 gallon gas tank (give or take - I think the exact specs say 11.9, but the gas bladder is collapsible and the general consensus is that a fill-up will take you just over 10 gallons, which has been our experience), which is psychologically rewarding in that when I fill up my tank I don't generally pay over $40. The better mileage we get, the less we have to stop and fill up. So we generally have to fill up about once every 10 - 12 days.

For a long while after we bought the Prius, our gas mileage hovered somewhere between 43 and 47 MPG, depending on the type of driving we did. The hybrid motor seems to do best in city conditions and stop-and-go traffic, since it can use the batteries more. Therefore, we typically get better mileage when driving in the city than we do on the highway.

Over the past few months, however, we've been trying to drive smarter - coast to stop lights and down hills, let the terrain help propel the vehicle rather than the gas pedal and, hardest of all - we've tried to slow down on the highway.

Driving 55 MPG on the highway saves gas. Period. Some really stupid people out there probably still "reason" that if they drive 70, they'll get to their destination faster, and won't be on the road as long, so they'll save gas, right? Wrong-o. A 2005 article in the San Francisco Chronicle puts it this way:
For every mile per hour faster than 55 mph, fuel economy drops by about 1 percent, said Jason Mark, clean vehicles program director for the Union of Concerned Scientists. The drop-off increases at a greater rate after 65 mph. The faster you go, the faster the fuel goes.
[Mark] figures that a commuter making a 30-mile drive to work at 65 mph instead of 75 mph would save about 30 cents in fuel costs per day -- or $150 a year -- and spend just 3 1/2 minutes more daily on the road.

But driving 55 has it's drawbacks. It takes longer to get places, for one. Then there's the people who get right up on your bumper like they want to drive right over you. Or the assholes in the SUVs and trucks who gun it past to make some sort of point. I laugh at the gunners - you just wasted money to try to piss me off. It didn't work. You happy now?

Since we used to drive about 65-70, we've been trying to pull that back to 58-60. And I think it's working.

We got 50.4 MPG on our last tank of gas - almost 500 miles - while running the air conditioner non-stop because it was so fracking hot outside.

There's always the talk about how the Prius isn't a good value because the price you pay for it vs. the savings in gas doesn't even out. I hate math, so I'm not going to run any numbers. What I do know is that I hate to put gas in the car, and I really hate putting over $80 worth in every 5-7 days (like we have to do with our Jeep Cherokee, which is why it gets driven about once a month). Forty dollars every 10-12 days vs. eighty dollars every 5-7 days seems like a pretty good deal to me. I also love the keyless entry and start, the navigation system, the back-up camera, and all the other bells and whistles that I smile about every day.

I'm not trying to get you to rush out and buy a Prius by any means. But I was so happy with our last tank of gas that I just had to tell someone. Who better than you? :)


  1. So you're the person going 55 on the highway! Totally kidding. We just drove to Iowa and back, averaging about you have me trying to crunch the numbers.

  2. I'm driving an SUV right now which just sucks the living daylights out of a gallon of gas (and my pocket book too) and I find I unconsciously go slower on the highway to save gas. Meanwhile the gf has a mini and when she lets me take that thing out I'll gun to 70 in third cause it's so damn fun.

    Point is, I always thought someone needs to make a car with the mpg of the Mini but makes you feel as guilty as driving an suv. That Prius computer would do the trick and I could see it becoming a competition to try and get more out of a tank of gas than the last one.

  3. As long as you are staying in the right lane....

  4. Congradulations on trying to make a difference by slowing down and seeing what it does for your fuel economy.

    I did a short test in my Civic Hybrid last summer - same stretch of hwy both ways at 55-70mph and AC ON (MAX) or OFF.

    - With AC ON the fuel economy dropped from 50 to 40 mpg going from 55 to 70 mph
    - With AC OFF the fuel economy dropped from 65 to 43 mpg going from 55 to 70 mph

    So, not only does speed hurt fuel economy for me, but using the AC hurts it by 3-15mpg as well. I try to stay below 60 with little if any AC these days. 55mpg for 32k miles so far.

  5. I started checking my speed a month or two back, dropping from 75+ to actually driving the speed limit on my 22-mile commute. The gas saving is nice, but I have also found any hint of road rage is gone and it's nice to not have to worry about speed traps.

    As for the Prius, we've been thinking long and hard about one as we get ready for a new car. I really like the one my friend out in CA has, but I can't justify the cost at the current levels of fuel economy it gets. My Matrix gets around 30mpg, so unless I'm driving like crazy, I still only fill up once a week for about $40. It might make more sense living in a place like CA where you can get tax breaks and carpool lane access just for driving a hybrid.

  6. When we bought our Prius last year, we got in on the tail-end of the federal tax break. I don't think one exists now, and that is a shameful shamey shame.