Fuel Efficiency Or Family Harmony?

While we were driving home from our Thanksgiving vacation today I had time to think, lots of time to think. I thought about how when I varied my speed I was able to vary my fuel efficiency.  Really, I coud vary my MPG my changing my MPH

Photo of Crazy Boot Truck on highway
Crazy Boot Truck in Connecticut
The LL Bean 100th Anniversary Boot Truck

Amazing that I could think with 6 people in the car! It was awesome, but we managed to get out just in time for our toddler’s nap time, the twins were absorbed in their Nintendo 3DS’s, Jon was writing a blog post and Cynthia is great at occupying herself in the car  (Cynthia is our family friend from Florida who is in college in Boston and joins us for Thanksgiving rather than flying home) even with 6 people, the car was pretty quiet for the first half of the trip.

So anyhow,  I had the opportunity to think about how my driving style affects the mileage I get when driving.  Most people are generally aware that when you drive in the stop and go traffic of “city” driving – more properly called “local” driving, your car is less efficient and you need more gas to go per mile, than when you are on the highway. You can also affect the mileage you get when on a highway by paying attention to how quickly you accelerate and how fast you go.

Accelerating quickly means you are making a big heavy object move faster, faster.  It takes more energy and therefore more gas to do that.  If you accelerate more slowly, it gives the car time to build momentum and you don’t need as much gas.

Today We were in heavy but moving traffic and I noticed that the car was averaging 19.1 MPG (which is pretty great for our minivan).  We were going with traffic between 50-60 MPH.   Then the traffic loosened up and I was able to speed up.  I was soon going about 75-80 MPH.  I was debating if it was too fast for Connecticut (they have very serious speeding enforcement there) versus the fact that I knew today was going to be a longer than average drive because of the heavy holiday traffic.  With six people in the car I knew the silence wouldn’t last forever, and the further I could get quickly the better off we would be for everyone’s sanity.

Then I noticed that our average mileage had already dropped to 18.9 MPG – this was over the entire 150 miles the car had driven since the last gas fill-up.  In just a few minutes, while going quickly, we had been getting such bad (or low) mileage that we had dropped the average mileage already.

Serious food for thought. While we had been traveling in heavy traffic, we had been driving at close to optimum speeds for fuel efficiency for our car – in general cars get their maximum fuel efficiency between 45 and 55 miles per hour.  When we sped up, it might be better for family harmony, but we were using a lot more gas to get where we were going.

Which to optimize for, fuel efficiency or family harmony?

cars in heavy traffic
Stop & Go Traffic

On this trip,  I erred on the side of family harmony, but when the traffic got heavy again, and we were back to 55 MPH, I was able to console myself with at least knowing that I was reducing our carbon footprint!

Of course, there’s the other end of the spectrum as well.  I’m actually writing this while Jon drives during the second half of the trip.  He was going 20MPH in very heavy traffic and now we’re in stop and go traffic leading up to the tolls.  Earlier we hit a maximum efficiency of around 21 MPG.   When we were crawling at 20 MPH we were getting around 15 MPG (which is still better than our typical city driving).  After 10 minutes of stop and go, we’re down to 9.9 MPG and it will continue to drop as we wait our turn to get onto the Mass Pike (and wait and wait and wait).

For more information on impacting your fuel economy,  stay tuned for Jon’s more technical post on maximizing your fuel economy.

Happy Greening,

Oil barrel with text In 2011, the US spent $460 billion on imported oil

Related Post: How much did the US spend on importing oil in 2011?

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