Did my first fill-up with my 2016 V that I bought with 7300 miles on it. The calculation yielded 35.7 mpg. However, the V's computer indicated it was 45.5 average for the tank. I didn't make any mistakes with fuel consumed, or miles traveled. This is just the first fill-up, so the numbers may converge in time, but I am disappointed with the large discrepancy between the math and the computer. My other Prius' were usually withing a mile or two of the computer estimate. -Bummed out in NC
On average you should expect the computer to be about 2mpg higher than actual. Apparently this is your 2nd fill-up not your first. If you didn't do the initial fill then the numbers mean nothing. In any case the only numbers that mean anything are averaged over multiple tanks.
That's a 27% discrepancy. Did you top it up at purchase, or is it the case that the seller said they would deliver it with a "full tank"? If the latter, likely it was a bit short of full, comparing to your fill-up technique. Next fill-up will tell.
The car came with full tank, but it had been test driven a lot, so wasn't really "full", therefore, mpg numbers would be unreliable. The second fill means nothing other than I know the tank was filled. It is my starting point. I did not begin my calculations until the third fill, which was yesterday. For some reason, Fuelly is not showing accurate fill numbers on my signature for the V. It should show "2", the number of times I have added fuel to the car.
**Edit** Fuelly might only consider a "Fuel-up" to be how many times it has calculated MPG. So, in that case, "1 Fuel-up" is correct. Not sure though why it is not showing what it calculated. At any rate, if you click on the Fuelly banner it will take you to the correct numbers.
FWIW our car computer seems to calculate the average MPG a bit high. 2-3 MPG higher than the manually calculated value I figure on fill ups.
If anyone reset the Trip & MPG display anytime later than the actual fillup time, erasing some trip miles for that tank, then your first fillup calculation will be bogus. It doesn't matter that the fuel gauge on the dashboard appeared full, 1-2 gallons could still have been missing. [I don't have signature messages displayed, so can't see your Fuelly record.]
That doesn't help in this situation, when the filling in question happened before he acquired the car. Absent these meter resets synchronized with refueling, the car's displayed MPG is also meaningless for comparison to hand calculated MPGs.
Relax. Focus on the results you get on the next few tank fill-ups. Look at those individual results. Your current results are probably skewed by events that occurred before you bought the car. My '12 v MPG varies greatly with low MPG fill ups following super high ones or sometimes the reverse. But over time, the average varies very little even though individual tanks can include only in-town, up to the mountains, off to the beach, mixed driving, just me or 5 people and stuff for us for a week. And pump shut-offs vary wildly as does the quickness of my hand at reacting to the click of the pump. Fast and I put in less gas and my MPG is high. Slow and I put in more and MPG is low. My last tank was 1.4 MPG better than my 42.0 MPG long term average and that variation didn't affect my long term average one bit because there were so many that built that average. The 42 average has included 17 and 72 MPG fill-ups, both highly suspect. The fuelly average tells the truth over time. And obviously driving style (I use ECO and Auto HVAV and just drive it normally. I'm not slow off stop lights nor do I slow others down.), tires (size and type), weather, terrain, etc all matter a bit.
