Search the Community

I did some more measuring and testing for the MPG crowd. Before I start I will say that I just verified my SGII and its right close to being on the money (off by 0.2 gallons). I'll assume that a slight error between the ScanGauge and the fuel pump. Now I my truck conditions are Edge set for 5x3, IAT fooled to 143*F, Engine coolant varied from 188*F to 197*F, winter fronts still on. Actual weather was high of 65*F (actual IAT was ~90-105*F) Now since I was on I-84 down in southern Idaho today I figure I open the beast up and let it fly low for once. So I set the cruise for 75 MPH and reset the current MPG counter and measure for about 20 miles of highway. I was pulling roughly ~13 MPG. Then after shopping in Nampa, ID and got back on the same stretch of highway again and set my cruise this time for 65 MPH then reset the ScanGauge II again and measured about 20 miles of highway again. I turned out ~18 MPG. Then even with all the playing driving fast and slower I still pulled in the yard with a total of 22 MPG. So from this rough measurement I found that roughly for every 10 MPH above 55 MPH I lose roughly 5 MPG. This is calculated numbers here. According to Google Maps its 300 miles round trip what I drove. Time to travel distance 300 miles / 55 MPH = 5.4 Hours 300 miles / 65 MPH = 4.6 Hours (0.8 hours less than 55 MPH) 300 miles / 75 MPH = 4.0 Hours (0.6 hours less than 65 MPH, 1.4 Hours less than 55 MPH) Amount of fuel consumed 300 miles / 21 MPG = 14.2 Gallons (@ 55 MPH - not a true 55 MPH because of testing) 300 miles / 18 MPG = 16.6 Gallons (@ 65 MPH) 300 miles / 13 MPG = 23.0 Gallons (@ 75 MPH) Cost difference @ $4.019 Gallon (which I paied for) 14.2 Gallons x $4.019 = $57.06 16.6 Gallons x $4.019 = $66.71 ($9.65 more than 55 MPH) 23.0 Gallons x $4.019 = $92.43 ($25.72 more that 65 MPH, $35.41 more than 55 MPH) Another tidbit. I get the same MPG's towing my RV at 55 MPH than I do driving empty at 75 MPH. Also the fuel consumption rate at 75 MPH is just about the same as climibng a 5% to 6% grade at 55 MPH. This shows that amount of rolling resistance and wind drag differences between 55 and 75 MPH.