I just filled my 2005 Prius tank the other day. I had just lost my second bar on the gauge and found it very confusing to have put in 10.88 gallons when the pump shut off. I usually get no more than 9.5 to 9.8 gallons when I fill up after the last bar starts blinking. Now that said, this tank is really going great guns. I didn't loose the first bar on this tank until I reached 206 miles! Usually I loose it at just over 100 to 110 miles and the next bar falls off in 44-48 more miles. However, I had the second bar fall off at 238 miles on this tank. This where the MFD consumption reports average milage at 49 MPG somewhat average for my driving over the last 7 tanks. I live in the SF Bay Area and the weather has been relatively stable this winter and early spring. Any thoughts as to why the difference in fillup amount and distance traveled and fuel gauge bars disappearing so slowly on this tank?
Wow, that's the opposite problem most of us have...too much gas going in in your case. The guage is notorioiusly inaccurate due to several factors, but the main one is the shrinking/expanding bladder within the tank.
On my recent trip I had the same thing occur. I think it's because the warmer weather makes the bladder more fexible and able to hold the full capacity. Also i found that at the very end of the fill up if you hold the handle of the nozzle up a little so the nozzle points down into the tank more you can get a really good fill up, maybe a gallon more than normal.
RadMarv - Your "usual" experience with the gas gauge bars is the same as mine ... a little over 100 miles when the first bar disappears, about 50 miles for the next. I had one tank last year where the first bar disappeared after 220 miles! I thought I'd get super high mileage on that tank, but the subsequent bars left at a faster pace than usual and I ended up with a "regular" tank MPG. Probably just a glitch in the software. I'm an electronics engineering technician, so I have a habit of blaming software first, anyway. - Ed
RadMarv, my experience with the bladder is much like what you are reporting on this most recent tank. My car is garaged both at home and work, and the ambient temps of those places is rarely below 50 degrees. So, when I fill up I'm generally filling up a vehicle with a relatively flexible bladder. I haven't experienced any burping or other fuel filling issues that others exhibit. And my conclusion is that because the vehicle is protected from random outside temperatures, specifically very cold temperatures for periods where it is parked the bladder is more agreeable when I get the car out and drive it.
Re: Fuel Gauge QUIRK FOLLOW UP! SHOCKED AND SURPRISED!!! I just filled up the tank today and even made an attempt to top off the tank this time to see what would happen. I had about 30 miles on the last BAR of the fuel gauge with it still not blinking. The fill up ended with 9.75 gallons. My milage for this tank was a whopping 529 miles. An average of 54.25 MPG! This is the longest distance I've gotten on a tank of gas and the best calculated MPG. The MFD calculation reported 47.7MPG. I am still surprised that today I filled up the tank during the warm part of the day here and most likely the warmest day yet MFD reported outside temp at 72 degrees. I made that last fill up in the coolness of the evening somewhere around 60 degrees. Not sure what sort of quirk I am seeing here.
Can't one design a system where the amount of gas (or gas usage for that matter) is determined by the weight of the fuel in the tank (what is it, 6.7 lbs/gallon?). It would seem to me that this would eliminate ANY discrepency due to the bladder, outside temp, etc.. If your tank weight increases 67 lbs., you've added 10 gallons. If it decreases by 33.5 lbs over 250 miles, you've used 5 gallons and gotten 50 miles per gallon. Maybe a weight system would be too complicated for a car as I am sure people much smarter than me have already thought of this and "shot it down." Don't mind me, I'm just ramblin'....
