Fuel Gage Oddity

I think the tank holds a little over 10 gallons of gas, so at 48.8 MPG, your range is around 480 miles per tank . 260 miles is around 55% of your tank, so, 4 pips left seems right.

 

48 MPG is not bad, I get 42 in my normal commute in my '09, dipping to 40 when it is over 95 degrees.
A wild number of variations in driving conditions and driving styles will prevent anyone from saying what you should get. High speeds will lower MPG, short trips will lower MPG, frequent braking will lower MPG. (I am suffering road construction on my normal commute, a bypass road posted at 45, with no stops is upping my average MPG to 47 but 'costing' me 15 minutes and extra 7 miles. I use less gas in my normal commute, but get worse MPG, be clear what your goals are)

On my '09, the fuel gauge is wildly variable, some times I can go 150 miles before the first pip is gone, sometimes the last pip only lasts 7 miles. I drive 400 miles and start looking for gas. My best tank is 480 miles. (I drive normally, no hypermileing that might invoke road rage in other drivers. They are already in road construction hell)

 

My understanding from other discussions is that the fuel gauge in gen 2 can be quite inaccurate but the problem has been fixed for gen 3. The gauge in my 2010 seems fairly accurate so far...

 

If you fill up when the last pip is blinking, there are about 2 gallons left. Seems to be typical of most cars we've had when they are at "E". The capacity is 11.9 gallons, I believe. I'm not sure what capacity the computer uses to calculate miles remaining.

 

On our first fill-up there was one pip left on the gauge. We had gone 438 miles and there was still 2.7 gallons left (took 9.2 on the fill). When you have one pip left on the gauge, you can probably go at least another 100 miles.

 

The gauge is accurate, in the sense that when it says you're about to run out you should pay attention, but the gauge is not linear. One pip near empty is much smaller than one pip near full. Also, the vapor recovery system and finicky gas pump nozzles often mean that you get less than 11.9 gallons in a fill. If you assume that you can always drive 100 miles or whatever when you have one pip left, sooner or later you will get a nasty surprise.

 

Fuel gauges are rarely linear. I assumed the car would warn you when you were getting near empty. When I saw one pip/bar left on the fuel gauge, I figured it was pretty low. I was very surprised it had nearly a quarter tank left.

In future, when that last pip/bar starts flashing, I'll find a nearby gas station.

 

I drove my Prius like a maniac this past Friday/Saturday, averaging about 65mph the entire trip and reaching about 90mph heading to our destination and reaching 75mph heading back from our destination. We also stopped by our old college and even drove around and looked at stuff, which was approximately half-way through the trip heading back.

The last fuel pip then started flashing when we finally reached the borders of our home city and decided to look for a gas station on the way to our house. Upon filling up, the meter read "9.337 gallons" so I made my calculations...

440 miles / 9.337 gallons = 47mpg!

Now the fuel trip display that measures how many more miles I can drive on the car said "42 miles." Should I have trusted this instead of chickening out and getting gas even though the fuel pip was already flashing? I'd approximate that I would've had another 10-13 miles to go from where I'd have to exit and fill up for gas.

 

I was also wondering about that Miles to Empty feature on the 2010 model as I was coming back a week ago from Kansas City - about 2:30 in the morning and the place I was going to fill up at on I-70 was closed for repairs, which I didn't expect.

I figured I could just make it to Junction City, about 40 miles with about 5 miles left in the tank. I did have some good 5 minute ranges of 100+ by driving slower and using the hills, etc., I didn't have to worry about a lot of traffic anyway, unless the cop would get me for driving too slow.

I got to Junction City and had about 13 miles left on the tank, so I did a little better job than I thought, but when I filled up I only got about 9.8 gals in the tank. I thought from the owner's manual is was a 12 gallon tank. So I'm not sure if it just a matter of calibration or the vehicle needing some more miles on it (was around 2300 miles at the time).

Max

 

You had at least 2 gallons left in the tank (11.99 - 9.337 = 2.563), which means you could run for more 94 miles (at 47 MPG). So I think the indication of "miles to empty" still leaves you with 1 gallon left when it reaches ZERO, just as a safety margin.

 

Very helpful information! Many thanks!

 

If you enjoy running out of fuel then go ahead and push the envelope. Otherwise, fill up when convenient, but always by one pip (not flashing!).

 

On my first tank with the fuel gauge flashing and the computer indicating that I had 25 miles to go, I decided to get gas first thing the next morning (my salesperson sternly warned me never to run out of gas!). When I started the car the next morning, the display said I has zero miles remaining! I drove about 5 miles for gas and was on pins and needles the whole time. I was able to add 10.157 gallons so it looks like I could have driven another 20-25 miles. Due to the inaccuracy of the gauge/miles remaining indicator, I will get gas in the future as soon as the indicator begins blinking which should mean I have well over one gallon remaining. Good luck everybody!

 

This reinforces what I mentioned above. When the "miles to empty" reaches zero, you likely still have 1 gallon left, so depending on your MPG you can drive anything from 40 to 60 miles from that point until it dies. I want to stress though, that no one should ever try to play the "guess-how-long-it-can-go" game because gauge accuracy, in any car for that matter, is far from perfect. I usually get gas when I have 1-2 pips left, don’t wait for the flashing warning.

In the country where I come from, you actually get a traffic ticket if you run out of gas because of the potential problems caused by a dead car on the middle of traffic.

 

Today as I was coming back from the dealer in PDX, having dealt with other issues (see separate posts : ), while calling Toyota Care about something else, I asked how much fuel remains when the last pip/bar starts flashing?

This seemed a reasonable request as every other car I have ever owned (about 10) including a Toyota Avalon and my current Honda CRV address the issue. The manuals always stated one or two gallons but the P manual is silent on the subject .

The lady told me Toyota could not comment on that information since it can vary so greatly; driving habits, sludge at the bottom (only have 830 miles), etc. I reiterated that I was not asking how many miles I had left but how many gallons . Turns out when I filled up 10 miles later, clicked full at 9.6 gallons (and graph went to full).

I should have been shocked but after calling last month to request the exact dimensions of the hood (to see if the specs matched the T Canada P), I was told Toyota did not give out that information.

I really luv luv luv driving my Prius and really don't don't don't love Toyota customer "care." I could almost accept them washing their hands of my initial issue and punting to the dealer, but when you cannot even get the most basic informational assistance...

 

Still don;t think it is that good..

I had the blip come on.. but knew more had to be in there.. went another 65 miles on the hwy and then filled up.. with 10.5 gallons.. so I still had about a gallon left..

So I still don;t trust it..

 

I never had the last pip flashing on me, but I can tell you from my experience that when you have just one non-flashing pip, you still have at least 2 gallons left.

 

GIII, model 2, ~700 miles on it now

My fuel guage goes down to one bar/pip after I pull out of my parking sport from overnight when the engine started up. I can't get that bad of milliage going down the freeway!

Speaking of freeway/regular to/from work driving, I do not think I will ever see the big numbers put up from other people - it seems that ~50mpg is about the best I can get in Puget Sound area of Seattle. That is runing in ECO mode most of the time with EV and PWR for those approtiate situations.....

 

I didn't check the miles to empty on the first fill-up (didn't know how to, LOL). But with one bar showing at 438 miles it took 9.2 gallons (47.6 avg mpg) so that left 2.7 which meant I should have been able to go at least another 100 miles.

It does indeed sound like the miles to empty calculation is based on leaving a gallon in the tank when it says zero.

The way my wife drives (light foot), I bet she'll beat the 50 mpg combined rating. In the Lexus RX400h, she beat the 25 mpg combined rating by over 3 mpg (according to the computer). Her commute is a combination of highway and city driving, some days the highway portion can be somewhat slow but in VA she gets to use the HOV lanes with the hybrid. That's why we bought the Lexus 2 years ago. We wouldn't own the Prius if not for the the cash for clunkers program, it was the perfect opportunity to get rid of our '94 Jeep (trade value of $1700 and we got the $4500).

When I fill the Prius again I'll do another manual calculation, compare it to the computer calculation, and check the miles to empty according to the computer. I'll report back.