So I decided to take advantage of a trip, and thought it would be a good chance to answer some questions I had in regards to the efficiency of drafting with P&G vs P&G with longer coast downs.The experiment was conducted as follows.
I filled up at the gas station that's about .2 miles from the on ramp just outside of Lowell, MI at 3:30 p.m. The temperature was 83F and tire pressure 60psi on the rears, 55 on fronts. I proceeded to enter the on ramp following a semi tractor that I was hoping would serve as a viable candidate for my test. Sure enough he was very consistent at a 55mph speed and I was able to do 60-50mph P&G for about 90% of my trip there. I was careful to maintain at least 3 car lengths, as I felt any less would be unsafe.
Average speed up and coast down was 15 seconds for each. I filled up just off the freeway for .846gal for a mpg total of 72.9mpg for portion A of the test.
I proceeded to do my errands in Lansing which was less than a mile from the fill station and just topped off again before heading home.
I started toward home on the B portion of my test at 6:45 p.m. with a temperate of 84F. I proceeded to speed up to 60mph and coasted down to 40mph each time
average speed up and coast was 30 seconds for each. I was able to hit my target 90%+ of the time and came close to hitting it on the times when I missed. A couple times I started my speed up early at 45mph because of traffic requirements, and likewise also allowed myself to coast to 35mph an equal number of times as traffic allowed to make up for the times when I had to start it earlier. All highway portion of this testing was done in 5th gear.
The B portion of the test required .728gal on 61.7 miles for a total of 84.75mpg. While I understand that this size sample is subject to potential fill errors, I did my best to fillup the exact same way and feel confident that I was able to glean some valuable insight into how to best maximize driving efficiency with my 93 Ford Festiva 5Speed. Hopefully this can be of some use to you
Results:
A portion (
60-50 P&G with drafting semi): 61.7 Miles on .864Gallons =
72.9mpg
B portion (
60-40 P&G no drafting): 61.7 Miles on .728Gallons =
84.75mpg
(For full details read above)
Feel free to ask any questions that I didn't answer in the description.
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