Zero Weight Project

One aspect of performance improvements is the effect on fuel economy. In some cases, increased air flow, reduced unsprung and reciprocal weight can have a positive impact how much gas you use. For the Zero Weight Project, i decided to document the MPG and see if there was any change at all. The first thing I decided to do is establish a baseline.

I recently found out that some people do not know how to calculate fuel economy. I have to admit, I was stunned. I also realized that some people are missing this critical tool they can use to monitor the status of their vehicle. Below is a quick tutorial on how I measure fuel economy. This is relatively easy to do as long as you follow the basic principles I have listed.

Measuring MPG (Miles per gallon)

1. Fill up your tank with gas. Let the pump stop on its own. (Letting the pump stop on its own increases the accuracy of your calculations)
2. Reset your trip odometer. If you do not have a trip odometer, write down your regular odometer mileage.
3. Drive the car. For the most consistent average, try get as close as possible to “E” or empty. (This last part is not necessary but does help in better averaging.)
4. Go back to the same gas station (Same pump if possible) and fill up. Let the pump stop on its own. (Letting the pump stop on its own increases the accuracy of your calculations)
5. Document how many miles you have driven.
6. Document how many gallons of fuel you needed to fill up.
7. Divide the number of miles driven by the number of gallons required to full up the tank. This is your fuel mileage.

First Results

• Miles Driven: 215.6
• Gallons used: 13.444
• MPG: 215.6/13.444 = 16.04 MPG
• Total Cost: $53.36 Ouch ($3.969 per gallon for 93 octane)
  
• Cost per mile: 53.36/215.6 = $0.25/Mile
  

Notes:

This mileage was a combination of 50% city and highway driving. As always, it was spirited. My next trip is to Indiana this weekend. It will be interesting to see how the mileage changes with 90%+ highway driving.

According to the 2003 Bureau of Transportation Statistics (BTS) Omnibus Household Survey, the average commute to work is 26 minute, 15 mile one-way trip to work. Based on my figures above, the an average RX8 commuter will spend $7.50 a day, 37.50 a week or $1875 a year (assuming two weeks vacation) in fuel costs alone.

An increase to 20 MPG would result in a annual cost savings of $371.25. Increasing mileage to 25 MPG would reduce fuel costs by $672. Of course, we did not buy a sports car for the fuel economy.