I am at about 3 months and 3,400 miles on my 2013 Prius C2 (my first Prius). When I press the "trip" button on the ECO Score screen I can see my lifetime average MPGs (because one of the trip counters I've never used). It is still climbing as I learn to drive the car. How long until you noticed it settle on a number? I might be able to make a good estimate based on what other drivers have seen. Also, are you able to see the lifetime MPGs from somewhere other than pressing the trip counter?
I reset mine, but at 10k it was still climbing above 55. But it was doing it much slower, probably .1 or .2 per tank. One thing that you will need to be aware of, the trip doesn't go above 10k. It will roll over to 0 again. The numbers will still be calculated, but they start getting a little wonky.
Dang. At least I guess I should have a settled mpg by then. I just like to have a definitive number when someone asks what I get for mpg.
Doesn't really settle for me. On my various 1-2 mile trips, I get 50 mpg...but on my 10-20 mile trips I get 70 mpg, so it fluctuates. Plus the car is so new so I figure it'll average out to a little over 60 mpg for some time.
The problem is that if you always get the same mileage per tank now and it's better than what you used to get then the lifetime average is only going to creep infinitesimally closer to your standard for each tank. It's going to take a long long time to actually get there. For example: If you got 58 mpg average for your first 2000 miles, and there after got a steady 62 mpg average, then after 4k miles your average will be 60 mpg, and after 20k miles 61.2, and after 200k miles 61.96, so it never really gets there. Though I guess, 61.96 would round up, so somewhere around 200k miles it might equal out on the display.
This. If you live in a place that gets cold expect to lose 10 - 15% of your mileage by the time it gets below freezing.
Since I got my c on January 3rd, I'm at 5300 mi., 55.3 mpg reported and still rising from my 45mpg winter, one ~63 mpg tank at a time. The past few tanks, the total reported mpgs have risen by .9, .8, .7, and .6. My goal by the end of the summer is 60, and hopefully not going below 55 throughout the winter/'til next summer. We'll see about that. Edit: Because of averages, of course, it'll change less and less as I go on, and I'm guessing it'll settle down tank-to-tank after about 15,000 miles, but it'll still drift up and down between the warm and cold halves of the year. That is, if it doesn't somehow get reset by then.
... oh to be at 5300 miles again... I just rolled over 11,100 on my way home today. I bought my car on January 11th...
I accidentally reset my trip 2 button after my first oil change. Now I reset it with each change (writing down the mileage). I reset trip 1 with each gas stop (i do not record those).
10k miles should be a decent estimate. That should be about 1 year of driving for me which will also cover the winter months. I'm at 64.3 mpg and it creeps up 0.1 mpg each day with my commute. Long highway trips on the weekends bring it down by about 0.1 mpg each time. 15% off of 65 mpg is only 55 mpg. Not looking forward to winter!
On the car, my lifetime mpg is actually still rising 0.1 mpg about once every month or two, even after more than year. It currently stands at 61.5 mpg. My fuelly average has settled pretty well around 59.4-59.5 mpg, however, and has been there for six months, maybe more.