Tuesday, May 09, 2006

Gas Mileage Experiment

So a couple weeks ago I saw a report on the news where the report claimed that you could see as much as a 31% improvement in gas mileage by accelerating and braking slowly, driving the speed limit, and keeping your windows rolled up and air conditioner off. 31% was a large number, and I really didn't believe that report so I decided to do my own experiment under my conditions.

My test consisted of the following:
1. Accelerate slowly, always keeping the RPMs below 2k
2. Observe the lights and let off the gas and coast to lights that were red
3. Use the vent, but not the A/C and keep the windows rolled up
4. Drive my "normal" route to and from work, which is a mix of city and highway driving

I typically get about 400 miles from a 21 gallon tank, or an average of roughly 19mpg.

My test results gave the following:

454.6 miles from 20.892 gallons or 21.75 mpg.
So I gained about 50 miles per fillup and about 2.75 mpg increase, which translates to about a 15% increase in fuel economy.

Not bad, but not 31% either. Being as I drive a full size pickup with a big V8 engine my results may be somewhat of an outlier, but regardless it does show a decent improvement.

Other thoughts on the experiment:
1. It wasn't easy to do. Accelerating slow and steady off the line is something I had to remind myself to do. I tried to be a right lane driver as much as possible, but still drew the ire of many speed demons. Jill told me that I was being the type of driver that drove her crazy.

2. It was very relaxing. Not launching off the line and cutting in and out of traffic really makes the drive very stress free. I would just focus on the aspects of the test and not worry about the other people around me, which made my drive very easy. Granted my drive isn't usually stressful, but you can make it as easy or as hard as you want.

3. I rarely was slower getting to/from places. I was interested to see how much slower I would arrive at work or home with this slower, more methodical driving pattern. What I found was that I often would roll through lights as the speed demons who blew by me would be sitting at the same light. I found I could just coast towards a light when it was red and slowly brake as to keep moving, and often it would go green before I came to a complete stop.

So the bottom line was I gained 55 miles from a tank of gas. At 20mpg, that is 2.75 gallons which at $2.75 per gallon means I save about $7.50 per tank. 2 tanks a month (guessing) for $15 per month savings over 12 months means I could save about $180 per year by driving in this manner. I'm going to go back to "normal" driving for this tank, then alternate driving methods between the test and normal for a few more tanks to ensure the validity of the test but I think I will find similar results in the coming few tanks of gas.

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