Fun with Excel and numbers...
On FuelEconomy.Gov, the fuel mileage testing establishes 21.2 MPH or lower as 100% City driving and 48.3 MPH and higher as 100% Highway driving. So using those figures, I was able to make a chart with percentages and then created a formula that would read it based upon the average speed of that tank of gas to establish what the ratio of city to highway driving was done.
Over the years there would be several similar average speeds for a tank of fuel but wildly different gas mileages and I did not know how to explain it. This information now gives me a better idea of how the truck was used during that tank of fuel.
The data below was from our trip to Ocala. At the end of the run the average speed was 46.3 miles an hour which is 92% of 48.3, the number established by the EPA for highway driving. I do not believe it is entirely accurate however. On this run my wife sat in the car for about an hour while we were inside the museum and then I sat in the car with my wife while the kids ran into a store to pick some things up. There was also 15 minutes at a rest stop. I'm guessing idle time was about 90 minutes compared with 3/4 of an hour doing the math. The day before this trip, my wife has also used the truck for errands; she idles away yakking on the phone and runs it like a scalded dog when going from A to B. I say this because the instant economy was 21 mpg and higher on the way up, the average climbing into the 18s when we arrived on station and was still in the 15s after idling in the museum parking lot and climbed back to 17 mpg by the time the truck was refueled.
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Anyhow, what do you think? Is there a way to possibly make this more accurate by the data provided by the DIC?