When I got my sg one of the first things I did was some measurements to get a better idea of what was the best speed for my 2005 Honda Accord. Then I used it to get some information on what was the the best route to take into work. I thought I would share the ideas and perhaps give others some idea to play with when they are deciding which route to take to various places.
The first test involved recording the instantaneous mpg at various points along my route to work. To control for variability I choose relatively flat areas, use the cruise control and picked about five locations to record the mpg. A digital recorder was very useful. I had assumed that somewhere around 55 mph was optimum. As it turned out 55 was better than 60 and 50 was better than 55. I have yet to test 45 vs 50 but I suspect that it is better still. So that was the fist surprise and is one of the reasons if fuss a bit that the EPA and the like to not really tell the full story on fuel efficiently.
The next test was a bit more complex. There are three main routes I can reasonable take into work. There are other options but I am pretty sure that none of those would be an improvement in terms of gas mileage or time. In the past I have always choose my route based to time.
Route 1 was my preferred route and was the fastest. It had the longest stretch of higher speed limits, fewer lights. It is about 17.5 miles long.
Route 2 is shorter, but adds in three lights - none of which are favorable to the way I approach the lights. Although at two of the lights I can make a right turn on red. It is slower than Route 1 by about a minute and adds about 2 miles of 40 mph two lane roads in place of the 55 mph limited access highway. It comes in at 16.5 miles
Route 3 is shorter still at 16.1 miles, but it is the slowest of the three routes. It just changes where I hit the main road so it replaces about 1.5 miles of 55 mph highway with about 1.1 mile of 40 mph two lane road. However it changes where I hit one of my lights and puts me at the unfavorable position at that light.
I spent four weeks to do the test by driving each route on each of the five days of the week. I had to extend it into the fourth week when I deleted a couple of days as it rained once and I was slowed by an accident once.
My assumption going in was the Route 1 would be the best choice since it had the time and open road advantages. That turned out not to be the case. Route 1 come in at about .50 gallons per trip with an average of about 35.5 mpg. Routes 2 and 3 came in at about .45 gallons per trip. Route 2 average about 36.5 mpg and route 3 averaged about 35.5 mpg.
So it looks like I'll be changing which way I head into work. The overall savings for route 2 are not great. It should save me about 12 gallons of gas a year. At the old $2.00 per gallon price this was $24 dollars a year. Of course now it is twice the cost.
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