Gas gauge frustration/inconsistency

I don't get it

 

welcome and congrats! 3/4 of a gallon isn't enough. you need a good 2 gallons to get the computers to register.

the best way to handle this is, figure out her average mpg. if it's 45, have her fill up at 400 miles or so. that leaves a fusion to look for gas. all the best.

 

Have her get in the habit of filling up at 2 pips. Running out is a bad thing, for several reasons, even if there is a spare can. Extra fuel is not a great thing to carry inside the vehicle, either.

 

When I was a teenager, I had a car with a broken gas gauge. I just memorized the odometer and filled up after a conservative number of accumulated miles. At no point did I think about carrying a dangerous smelly gallon of gas in the trunk. Occasionally, when someone borrows the car or I have no idea when I last filled up, I drove to the gas station.

 

And, it may require as much as four gallons for the fuel gauge to register. So now the wife has to pour the 3/4 gallon of fuel into the fuel filler, probably spilling some of it on the side of the car. Then she has to disconnect the 12V battery so that the engine ECU which logged an out of fuel DTC, and the fuel gauge will both reset. Until they are reset the Prius will refuse any attempt to start, to protect the traction battery state of charge.

Hopefully she doesn't cause a spark which causes the accumulated fuel vapors to blow her up, not to mention the Prius.

Far easier to refuel no later than when the fuel gauge shows two bars, as previously suggested. Also, use the MFD mpg gauge and trip odometer as another means to determine fuel consumed since last refill, and fill at least that amount when refueling.

 

Op doesn't mention the bladder, I will.
When it drops below ?60 degrees the bladder inside the gas tank starts to shrink, when it gets below 32 the bladder has shrunk, now the tank holds less gass and your assumption of how far is skewed, just sayin

 

My 2008 Prius goes down to 1 pip then the single pip starts flashing.. I know then I'd better stop at the next filling station.. I wasn't trying to run out but I was listening for a warning beep. I was told that there is a warning beep when the last pip starts flashing.. I have never heard the beep so I guess it must be a short one and the radio was too loud