Number of trips so far: 46

Average Speed: 54 MPH

Average Trip Length: 49 Minutes

Average Fuel Economy: 36.6 Miles Per Gallon (MPG) with a Std Deviation of 2.46 MPG

I should mention that my average speed is low since a portion of my trip is through slower roads, stoplights, and stop signs. I normally try to drive at a very constant speed of 60, 65, or 70 MPH for most of my trip.

For now, I looked at 4 different parameters that may or may not correlate well with my fuel economy. These include Average Speed, Air Temperature, Warm Tire Pressure, and Relative Humidity…I’ve graphed the data below:

Miles Per Gallon as a function of Average Speed

Speed:  Average – 54 MPH Std Deviation – 3.75  Correlation -  -0.203

Miles Per Gallon as a function of Air Temperature

Air Temperature:  Average – 17°F Std Deviation – 12.7  Correlation -  0.504

Miles Per Gallon as a function of Warm Tire Pressure

Warm Tire Pressure:  Average -  35.8 lbs Std Deviation – 1.12 Correlation -  0.477

Miles Per Gallon as a function of Relative Humidity

Relative Humidity:  Average – 76%  Std Deviation – 12.95 Correlation -  0.012

What can we determine from the data?

I’ve included an Excel guess at a 2nd Order Polynomial equation trend line for each of the graphs. Based on this as well as the correlation data, it seems tire pressure and air temperature play a significant role in fuel economy. Obviously, speed plays a large role in fuel economy as well. However, I don’t think we can take much from Relative Humidity (RH) just yet…There simply isn’t enough data and it doesn’t correlate well.

I suppose what intrigued me most were the trend lines for temperature and speed. The mileage trend appears to have a maximum of approximately 40 MPH and trails off fairly fast as speed increases. Also, fuel economy seems to trend upwards as air temperature increases. It would be interesting to see where the top of that curve is. Unfortunately, I’ll have to wait till warmer weather before I can drive in warmer temperatures.

Let’s make a few assumptions (we’ll have more data later on) on gas mileage:

• The best fuel economy is around 40 MPH and falls fast as speed increases

• As temperature decreases, fuel economy tends to decrease

• Mileage appears to increase with an increase in tire pressure

• Humidity may affect fuel economy, but more data is needed.

A couple of notes:

1. Most of this information is common knowledge, but basically what we’re setting up here is a baseline for further data-gathering on my commuting trips.
2. Also, any wind effects are not taken into account for the above data. I’ve tried to record wind data, but gusting and changes in direction of travel and wind make it difficult to accurately reflect the effects of wind on fuel economy.