Driving habits make big difference in my MPG

August 18, 2007

I test-drove some “mpg caps” last summer in an effort to determine whether they delivered any benefit. My results after one month of driving were pretty abysmal. Before the test, I tested my driving for a month and was getting around 23 mpg. During the test I got between 23 mpg and almost 25 mpg. It’s not bad, but not much difference. The cost of the pills negated any cost savings on gas. I tried to maintain the same driving habits during those two tests to minimize differences. Weather may have played a factor a bit, but the pills didn’t make enough difference to justify buying them (and I’m still not 100% convinced they had any real benefit anyway).

Fast forward a year. I’ve been concerned about changing cars. I have a lease which I’m ending, and I’ve been undecided as to whether I should just buy the car or turn it in and get something smaller. One of the primary factors in my decision was mpg With gas costs having gone up around 70% since I first got the car, the cost of driving, especially to my new job, are a lot more top of mind. So I’ve been reading up on ‘hypermiling’.

“Hypermiling” is a term coined by hybrid drivers focused on maximizing their miles per gallon. I thought I’d apply some of the same techniques to my driving habits to see the results. I know this isn’t necessarily all that statistically accurate, it’s the same mpg test math I did last year. I’ve gone from 22-24 mpg to 31 mpg by changing my driving habits.  (note: last fillup was 7.5 gallons and I’d done 230 miles - 30.7 mpg - previous fillup was 31.5 mpg).

• I’ve slowed down. I obey the speed limit, and often go slightly under. I occasionally have to speed up to avoid annoying the drivers around me.
• I look for any opportunity to ‘coast’ - any stretch where I can maintain the same speed within a few mph range without having to give any gas.
• I turn off the car at stop lights where I know the wait time will be > 45 seconds. Some lights are 90 seconds or more, which seems to make sense. I’m not sure on the 45 seconds cutoff. Am I wasting more gas by restarting the car?
• I turn off the A/C. This has been hard the last couple weeks. I don’t have it off completely, I just don’t run it the full time I’m driving. I’ll alternate between windows down during slow driving and stops, and toggle the A/C on/off every minute or so.

I think by October I won’t need the A/C at all, so that shouldn’t be a factor at all, and I’ll probably get consistently higher mpg.

I have been amazed at how much more mpg I can get in a 2004 Chrysler Sebring - rated at 18 city / 26 highway. This just makes me think of how much more gas we’d all be saving if all drivers followed these tips - slow down a bit, don’t race to red lights, etc. If I can realized a roughly 30% increase, couldn’t everyone? What if it was only 20%? Or 10%? What would that do to our dependence on foreign oil? To the rest of the economy given the extra money people would have by using less gas?

Posted in Energy, Personal, Travel