I have had my prius II for 3300 miles now and have found something interesting. the amount of gas that goes into the tank doesn't seem to be consistent. i realized this after filling up gas right after it dropped one bar. only 2.8 gallons went in but i had travelled 241 miles. i don't think i was achieving 80+mpg. the second time i tried this i had travelled 162 miles and 3.05 gallons went in after the first bar drop. i think the amount of gas that i can squeeze into the tank depends on the filling station as i think it is stopping prematurely. i read of this problem in the other threads but seems like they solved this problem for the new priuses. anyone else having a silmilar problem?

Yeah, i was confused about this too when i first bought the car back in march. I did some reading around this forum and found out that the prius gas tank is actually a "rubber bladder" which means it expands as you fill it up and contracts as it uses up the gas. this ensures that there is very little air in the tank at all times thus prevents air and moisture build up inside the fuel tank. So that means that you may not be able to fully expand the rubber bladder when you fill. For me, i can tell if the bladder didnt fill up all the way because the fuel bar goes down from 10(full) to 9 when i reach 150km (94mi) and when i am lucky enough to fill it all the way, the bar goes from 10 - 9 bars in 250km (156mi). Overall this doenst affect mileage you shouldnt worry too much about it.

This has been discussed many times on this and other sites. Your Prius is fitted with a "bladder" inside the gas tank (this prevents vapors escaping into the air). It gets stiff in colder weather. You should assume that the nominal 11.9 gallon capacity is not totally useable as the tank cannot always be completely filled. Assume a capacity of only 10 gallons in the winter ... a little more in the summer.

JeffD

I guess I still have an unanswered question in this thread. If I am down to 1 bar, and there is no gas station for a while, should I be worried? If we assume the average on the dash is correct (45 mpg, to be on the conservative side), how much do I have left before I completely run out, and have to call 911?

Ron,

The Prius gas guage is nortoriously inaccurate (particularly in the '04 and early '05 models, there is a TSB to improve it if your early NW20 is still in warantee - mine isn't. You have to complain about your gas gauge to the dealed to activate the TSB).

Once the blinking starts, you normally have between 50 to 100 miles of gas left, but don't push it. Running out of gas in a Prius is not a good idea. Your MPG indicator is a little optimistic (mine averages 1-2 MPG higher than actual) and your tank capacity is variable. Don't assume that you can easily make 500 miles on a tank (although in the summer I have gone over 550, but that was foolishly as a new Prius owner).

JeffD

Ok, stupid question coming .... what's a TSB?

Technical Service Bulletin. It's a communication update (aka technical notice) from the manufacturer on known issues (problems) and any resolutions (fixes) for those known issues.

We're consumers. We are by-products of a lifestyle obsession. Murder, crime, poverty; these things don't concern me. What concerns me are celebrity magazines, television with 500 channels, some guy's name on my underwear. Rogaine, Viagra, Olestra.
--Tyler Durden

The third time I filled up the tank I tried to get a full 11+ gallons. It was a warm day. I continued to manual fill after the click stop; I did a couple of pulses with additional click stops at the pump. Suddenly, the gas started pouring out of the filler! I had overfilled it.....what happened was that the bladder was moving a bit and a lot of gas was pushed out of the filler cap, onto the side of the car and onto the ground......
Yes, I felt a bit stupid after that. I cleaned it up and, low and behold, I got about 550 on that tank with one bar left.

I started at 4 miles with a full tank. Four tanks since then, and here's the trip mileage when each bar drops:


125 160 180 190 260 270 - 7.005 gals
165 195 220 245 280 310 355 415 460 - 10.468 gals
135 155 180 215 265 - 6.297 gals
155 185 205 230 260 290 320 - 7.598 gals

These numbers are approximate, but they're pretty close. As you can see, the first bar drops after anywhere from 125-165 miles, then 20-30 miles later, then 20-25, 10-35, 30-50, 10-30, etc. That's a pretty big variation. Remember how on analog fuel gauges a fillup puts you above the F line? Maybe we're seeing the same thing here.

Change what & how I drive, not who I am. Rack 'em up.