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Discussion Starter #1 (Edited)
I recently returned from a two week trip from Virginia to the mid-west (Oklahoma, Nebraska, etc) and back. 3396 miles total. This was my first long trip to see what kind of mileage my 2017 Pacifica Touring-L would get on the road. Also, I was curious how the trip mileage reported by the car's computer compared to actual. Here's my spreadsheet of results. For each tank of gas I reset the trip mileage counter after recording the trip miles and reported mpg.

The colums, in order are:
Odometer reading
Tank miles by subtracting odometer readings
Tank miles from trip counter
Actual fuel gallons
Calculated mileage using trip miles and actual gallons
Computer calculated miles per gallon
Estimated gallons of gas used according to the computer (trip miles divided by computer calculated mileage)

Summary/results: actual trip average mileage: 26.6
Actual fuel used: 127.57 gallons
Estimated fuel by van computer: 123.48 gallons
Computer avg trip mileage: 27.5 (using the estimated gallons)
Computer mileage error: 3.3% high

I thought the computer had been more optimistic than that - just over 3% error is not bad.

Some of those tanks of gas were almost all local/slow/stop and start driving. Out of 9 tanks of fuel, the computer told me I had averaged 28 mpg or better for 6 of them. For actual mileage I got better than 28 on only one tank, but 5 of the 9 were over 27, and 2 more pretty close to 27. For just road miles, without the local driving days, I'm pretty certain the average was well over 27. And that includes some hilly terrain at the beginning and end of the trip, some substantial head and tail winds in the midwest, and cruise control speeds of 70 to 80 mph wherever possible (generally speed limit+5)

Note: I saw in a different thread where there was some discussion about the computer estimated mileage accuracy being dependent on things like tire size, pressure, etc. I disagree. The same distance is being used by the computer as you would use to calculate actual mileage. Now, that measured distance may or may not be accurate, but the mileage calculated by using the odometer mileage and the mileage calculated by the car's computer should be consistent - regardless of whether you have roller skate wheels or truck tires on it.

Richard Cobb
 

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