calculated vs. computer MPG - Please post your results

Obviously the actual total tank capacity is considerably greater than the claimed capacity, as on most cars.
No, there will never be a way a car can accurately predict how far you will go on remaining fuel, even if the amount of fuel is known.
I have never seen fuel consumption as thirsty as yours, except on very short trips.

 

I don't get what you are saying here. Isn't the tank capacity published in the spec for any cars? Are you saying they are not the actual total tank capacity? Am I missing something?

 

Yes, the published figure is a lie, but it's a lie in your favor, because they don't want you to run out. The grand total tank capacity is the claimed figure plus the amount by which you can overfill it plus some additional safety margin. My owners manual states there is 1.6 gallons left when the last gauge segment starts blinking. Experiments (not by me!) have shown there's actually more than that, possibly 2.5 gallons.

 

Humm, I know that the tank empty light comes on alway before the tank is really empty as it should, but I have never able to put more gas into the tank than the spec total capacity in any car I have owned.

 

But you do not know how much you could've put in if it had been truly empty.

 

True. I always assumed the published tank capacity to be true full capacity. I have driven my current car PRIME ~100 miles after the tank empty light came on, yet the tank still took less than the published full tank capacity. If you are correct, I could have gone 200 miles or more after the empty light and could have filled the tank with more gas than the published full tank capacity.

 

I don't see why they would lie about this.

 

Don't forget; we're not talking about how much is left when the gauge says zero. Someone apparently put over 14 gallons into a tank that has a claimed capacity of 11.9 gallons. That's over four two gallons more than it's supposed to hold, which is 1/3 more than the max. That's a lot!

Edit to fix dumb math typo. Thanks for catching that, @Salamander_King.

 

Not trying to nitpick, but ... 14 gallons into 11.9 gallons tank is slightly over 2 gallon, not "over four gallons more". Yeah that is still a lot, I agree with you that the pump was wrong on this instance.

That being said, I think the spec tank capacity does not including any amount of fuel that can be in the pipe attached. If one top off and fills up the gas to the rim though it is a very bad practice, the total capacity maybe bit more than published spec. Still I don't think the pipe can hold 2 gallons more.

 

That "bad practice"can add at least 2 gallons after a typical pump shuts off the first time, I think I read in a long-ago post. That's not even counting the extra safety margin they allow at the bottom end.

 

Well, at least not for any of the previous cars I have owned including Sienna, Civic, or Gen3 Prius, I use to top off all the time. For those cars and all of the other cars I have owned, from the point of auto shut off to the point the gas may start to flow over is less than a half-gallon more like a quarter of a gallon.

 

Obviously you'll get overflow if you try to rush the "top-off.". To get in the maximum, one has to go slowly and wait a few seconds between small additions. I don't recommend going that far, but I've gone part-way many times, well beyond the quart you are claiming is the limit.
Wayne Gerdes has been known to shake the car for max fill.

 

Records reveal that when the last segment begins to flicker in my 2011, about 9.4 gallons is required to fill to the point that a typical pump shuts off. Add to that amount the 2.5 gallons reportedly left when flickering begins, and we get 11.9--- exactly the claimed capacity, strangely enough.

 

That has been my experience.

 

Last tank the computer said I got 50.3 mpg, but my real calculated fuel economy was 47.7879687079 mpg.
354.3 miles driven and filled up with 7.414 gallons of gas at Costco.

 

My calculated (actual miles per actual gallon) mpg's values are consistently 5-6% below the trip computer.

 

Over the life of my 2010 Prius, the average error is 6.49% too high on the computer compared with actual mileage.

 

Hello,

Here my concern, I hope someone can give an opinion or any feedback would be highly appreciated.

I have a 2014 Gen 3 Prius with currently 82-83kk miles. I bought it second hand 1 year ago with 73k Miles. So far I have been averaging a mileage of around 45 mpg (already lower than what I see reading here you guys average) and I consider myself a person that drives smooth and carefully. One month ago I brought my car to a Toyota dealership for its 82k miles services. Since then my dashboard average would barely go over 41.5 mpg. I put on fuel yesterday after 360.8 miles had a remaining range of 40 miles and it took 9.68 gallons, dashboard market then 41.7 mpg. If I do the calculations it gives me 360.8 / 9.68 = 37,27 real MPG. This seems for me a significant low MPG for a Prius and especially even more after reading anybody else average. Do you think my car is having any issues? I don't have any check engine lights on. They suggested to me at the dealership to do a fuel induction service that has never been done before. Would this help to increase fuel efficiency?

Thank you in advance for any feedback.