Finally got an opportunity to do this today! Took a little road trip over to Orlando (5-year driving instructor recertification class). Went a little something like this:
I hate driving on the interstate if I can avoid it, so I took a back roads route. The route I took was about 5 miles longer and took 40 minutes longer than the interstate route, but it's a much nicer drive. Or so I would normally think. As it turned out, the morning drive was about half good. I had to be there at 8am, so I left home at 5:30. It was a typical Sunday morning on back roads until I got about 45 minutes outside of Orlando about about 7am... then, it suddenly felt like rush hour on a weekday! And the trip home was about the same the whole way. Lots of unrelenting traffic.
In the morning, I was sort of trying to hypermile, but I was also in a hurry trying to make sure I wasn't late. Average speed for the ~2.5 hour trip was right about 50 mph. But, with parts of it being 35-45 mph roads, and parts of it being 55-60 mph road... that meant some cruising at 60 mph to make time. There was also some heavy rain at one point.
In the afternoon, I was tired, and just wanted to get home... but, not so bad that I took I-4. Took almost the same back roads route back. Traffic was awful, so it was hard to maintain a "slowish" speed, and almost impossible to do any pulse-and-glide most of the time. I did manage to drive a little slower in some places. My morning pace was 6 minutes ahead of the Google estimate, afternoon was nearly 10 minutes behind. Also some light rain.
Suffice it to say, conditions and mood were not optimal for hypermiling.
The stats were a little depressing:
Morning
122.4 miles
46.7 mpg on the display
Afternoon
108 miles
48.1 mpg on the display
That averages to 47.4 mpg from the onboard display for the day.
I filled up last night before I left, which is part of why the morning trip miles are longer. And I filled up at the same gas station when I got home. Not the same pump, though. That one was occupied. It's a fairly new gas station, though... should be consistent? Maybe?
So, 47.4 from the OBD.
Actual fuel used was 5.124 gallons.
By the trip meter:
226.5miles/5.124gals = 44.20 mpg
By Google Maps of my exact route: (should be more accurate)
230.4miles/5.124gals = 44.96
I expected the OBD display to not be 100% accurate, but it's off by more than I expected. Nearly 5% optimistic. But, it would only take a 2/10th of a gallon variance in fill-up to balance it out, so there's that possibility.
Bottom line from this trip: What I already knew. The Mirage fuel economy takes a dive at anything over 55 mph. Its sweet spot ends right about 50 mph.