Results! May Experiment!
By Karina | June 4, 2008
So I’m sure you’ve all been waiting with ‘baited breath for the exciting results of my May experiment (mid-month update here) to drive the speed limit! I am so totally excited, check out these numbers:
March-April Average = 58.24 mpg
May Average = 66.36 mpg
Which is a 14% Difference.
That is so huge! A 14% difference in fuel efficiency just because I drove a little slower! And I will add here, by the way, that I did my best to drive the speed limit but I was generally driving within 5 miles of the speed limit, and that there were at least 1 or 2 trips that were a little faster than originally planned because I was in a big hurry. And still!
Look, a graph! Now, I don’t have a lot of data points - this is where my exceptional mileage works AGAINST me, as I only had to fill up my tank 5 times. Um. I’m not complaining. I drove 2,348 miles during the course of this experiment.
I should note that my car is *really light.* And I know that that’s the number one reason why it is so efficient - the thing is made out of plastic and aluminum, you know? So the undersized hybrid engine helps, but because the car is so light it is very responsive to changes in driving patterns. Most people will probably not get a gain of 14% by driving slower. But I bet if they drive slower they will still definately see results - the Government lists a range of 7 to 23%, so there’s got to be something, right?
So what’s next? How about a June challenge! They say that 3% efficiency is lost because of underinflated tires, and the NHTSA estimates that 1.2 BILLION GALLONS is wasted annual because of under-inflated tires! Monday night I checked my tire pressure — which was super low, at 35 psi all around — and inflated the tires. There is some discussion out there on if a tiny bit of over-inflation is appropriate - it gives you slightly better gas mileage, but it’s a little bit less safe, too. I am over-inflating my tires. They’re rated at 38 psi front/35 psi back and I’ve inflated them to 40 and 36, respectively. I also started to use these LCD tire pressure gauges, which will flash if I am under inflated. I calibrated them to flash when the tires hit the recommended pressure. Now I just have to remember to walk around my car every day to check for inflation issues.
The best thing about the success of my May Experiment is that now I am consistently getting over 60 mpg, I am confident putting the 60+ mpg sticker back on my car. Here’s the thing - I don’t want to rub it in, but I *do* want people to know that it is possible for cars to be more efficient, and that they should be demanding cars that get over 30 mph. I know that the immediacy of higher gas prices is affecting the American people, but I don’t want them to put the blame entirely on refineries, or on oil executives, or on politicians who don’t want to get rid of the gas tax. The blame is on all of us, and on the big car manufacturers, for getting lazy and for avoiding efficiency and innovation.
Have any of you partaken in this kind of experiment? What did you think?
Topics: Transportation |
I think you should keep your tires slightly underinflated, just so those LED gauges blink constantly. Would be almost as good as hydraulics.
that would be so fresh. you know what? I bet if I drive below the speed limit so everyone can see the flashing better I’d make up for lost mileage based on underinflated tires.
We tried the same experiment! We have an early 2000’s v6. The results weren’t as dramatic, but we saw a significant increase in efficiency (avg. of 3 miles per gallon). Every little bit helps.
3 mpg is awesome, though! do a percent difference over what you were getting before, I bet it’s at least 10% better!
I’m really impressed with your follow-through on this issue. Those tiny choices add up!
wow, thanks! it’s amazing how the littlest things can be so measurable and impactful.
I have been trying to change some of my driving habits to see if the change helps my mpg. Interestingly, changing my route home seems to have been the most help. I can elect to use either a highway or only surface streets for my commute. I have found I get better mileage on the surface streets. Using streets on my way home is a very dramatic improvement because where I work is at a higher elevation than where I live so I can coast without much effect on my speed for surprisingly long periods. I don’t think that the highway driving is actually the culprit but the routes I need to take to get on the highway and the route to my final destination after the highway. And either highway or surface streets take me the same amount of time - probably having to stop for fewer lights driving all surface streets helps with both mpg and time.
In general I am coasting more and trying “driving with load” which is very counter-intuitive for me, you accelerate downhill and coast (as much as possible) uphill. Since I don’t do that when there are cars close behind me I haven’t tried it out enough to know if it really helps. Another version of that for flatter areas is “Pulse and Coast” which works because the mpg you get when pulsing (accelerating) for a few seconds is averaged with the high mpg you get when you coast — again not something I do when anyone is behind me or driving with me and might be affected by my inconsistent speed.
I don’t have a graph but my mpg before I started was 42 and 300 miles later (about three weeks) it is 49.
that’s so exciting, Harper! thanks for the input!
I have been trying to slow down and drive closer to 60 MPH on the freeways - speed limit here in Massachusetts is 65, and though I’m sure everyone else would love to go 80, 60 is about the average speed during rush hour home so I’m not slowing things down. I have seen a lot of like minded people in the slow lane lately!
One caveat on the May mpg improvement: summer blend gasoline. I just found your site, so (sorry!) I haven’t sorted out where you drive, but here in MA we do reformulate in the summer. You can see my January 2005-June 2007 chart from fueleconomy.gov here, with the peaks around July, and valleys in December. So if your mpg starts to drop around Halloween, it may not be that you’ve developed a lead foot, it might be the gasoline’s fault.
Now to get my average up above 40 so I can slap one of those 40+ mpg stickers on my car… :-)
in NJ we reformulate too, so that is definately an additive. I think the cold weather is a big impact too - lots of people add a piece of cardboard right behind their front grill, for example, to get the engine hotter faster in the winter, or some people even use a block heater!
congrats on your awesome mileage have you seen ecomodder.com? they have lots of great tips there.
[…] Results! May Experiment! […]
[…] letting us know about their campaign to, well, Drive Smarter. This definately ties into my recent experimenting with driving techniques to get better gas […]
[…] been telling people lately that I get great gas mileage because I drive like a Granny. I don’t know where that came from, really: for example, my […]