No low fuel light in Prius

One of my dads old beetles had a lever that you flipped when you were low on fuel, so you had that little reserve to get to a gas station.

 

Take a look at the spreadsheet with all the known Xgauges here; Fuel level is on rows 78 (liters) and 79 (gallons).

 

Unless I'm missing something, he's not in a Prius c.

That said, filling up 9 gallons when the bar starts blinking is about right, in my experience. I almost always fill up between 9 and 10 gallons, and I often run for ~50 miles after the bar starts blinking, depending on how nervous my wife is getting in the passenger seat (and what penance I would have to pay should the tank run dry in her presence...).

You can get more if you run it lower, or if you top off several times (though you might just be pumping fuel into the charcoal canister at that point). Percentage-wise, there is a fair amount of reserve left. There is also probably some unusable fuel on the bottom, depending on the geometry of the tank and what sort of slope (or acceleration) your car is being subjected to. I imagine that if there's only a gallon or so on the bottom, it's pretty easy for the gas to slosh around enough that the fuel pump will start picking up air.

 

Fuel pumps rely on fuel to cool the pump motor. No gas = warming up the fuel pump motor which isn't a good idea for long fuel pump life

Mike

Mobile on my SGH-i717

 

I did not know that. Thanks.

 

yes, I have the regular Prius. Still find it interesting that the fuel bar blinks even when there's a quarter of a tank left.

 

Quick question does the DTE show up when the gas gets low or is there a place or way of viewing it??? I have a 2010 Prius Four??? Thanks

 

The DTE is in the same place as the trip odometers, Just push the button on the steering wheel until it shows up.

 

You can press "TRIP" on the steering wheel until you see it. I wanna say it automatically shows up when you are near zero but I may be confusing it to another car. I'm not in the habit of driving DTE to nothing, so I don't remember exactly.

It's also shown on the lower right of the touchscreen when you press "CAR." On 2012 models anyway, pretty sure same on older models equipped with a touchscreen.

 

That's what I've been thinking since I got 07 Prius couple months ago! Filling up and putting in between 8.5 and 9.5 gallons. Driving me a little batty thinking about how much further I could go with a tank capacity of 11.9 gal. (I stop pumping at the first shut-off to try to get as consistent as I can figuring mileage. I know stations and pumps are not consistent, but I'm trying.)

So when last pip started blinking a few days ago at 438 miles and display showing 47 mpg on this tank, I figured I could go another gallon and a half, or about 70 more miles. I have read on here somewhere that you can probably go your display mileage times 10 gallons no problem. I debated whether I should stop at 470 or take it on to 500 or more.

I know a lot of people on here say the low fuel warning is more than sufficient, but to me it's not a low fuel warning if it kicks on too early -- it's an almost-but-not-really-yet-getting-low-warning! 3 gallons left is not low fuel in my thinking.

So on my way to work this morning, at 502.5 miles on the tank, with display reading 47.3 mpg, my car display lit up like the 4th of July. The Master Warning Light came on along with several others. Now I wish I would have taken more time to look at the display/messages, but I just assumed it was yelling at me about needing fuel. I ducked into the closest gas station with decent prices, just kidding, the closest station, and filled er up. I only went about a 10th of a mile to get gas.

Everything seems to be back to normal after getting gas. Calculating by fuel added, I got 47.9 mpg on the tank. But how much fuel did I add (to the first pump shut-off) ... 10.497 gal.

I think I have discovered where half of your missing quarter tank is. It's between the last pip and the display fireworks. Does that mean that the other missing 8th of a tank is found by continuing to pump after that first shut off?

I keep reading on here about topping off and why it is and why it isn't a good idea. So I don't know what to believe. I want to top off so I can better figure my mileage more accurately. I also want to top off so I can get closer to utilizing a 11.9 gal tank, not a 9 or 10 gal tank. Isn't it more efficient to stop for gas less, and isn't more efficiency part of the magic of the Prius?

My plan is either to keep filling up to first pump shut-off and then stopping for gas at display mileage x 10 (47.5 x 10 = 475 miles) or maybe I'll try pumping an extra gallon after first pump shut-off and then going x 11. I don't know yet.

 

Little bit more background to my post above... My previous tank took 10.5 gal to fill up when I thought it would only take a little over 9.5. I think that pump was set to shut off later. My display was reading 49.1 but calculated to be only 44.4. Usually they are much closer to each other than that. -- So when a typical tank took 9.5 to fill up and then this previous one took 10.5, it was closer to tank capacity than I was used to. I'm guessing that instead of the typical 2.5 gallons hiding out somewhere I was closer to only 1.5 gallons in hiding, leaving me with less than I thought I had when the last pip started blinking.

Did that make sense? Instead of having the usual 2.5 gallons left at last pip, maybe I only had 1.5, which I used when I went from 438 to 502 miles. I don't know. Maybe it's best to stop at mileage x 10 since I don't know how full the tank is without topping off. ??

 

Two more reasons why it's not a good reason to top off, beyond the one you've probably heard about filling the charcoal canister with fuel:
If you top off and spill fuel, it can damage the paint.
Topping off also leaves more fuel that gets evaporated, also generally from spills. Fuel vapors are a pretty nasty pollutant, even in small quantities - for that reason, a number of areas require that all gas stations have vapor recovery systems that sucks up the fuel vapors coming out of the gas tank. But if you spill gas, the vapors will enter the atmosphere (or the gas might be washed into the gutters), even if there's a vapor recovery system.

Best to not top off. If you really want better accuracy, then try filling up at the same gas station (and pump) every time. That'll probably get you a more accurate result than topping off at different stations, since the pump, nozzle, and slope of the ground will be different. You might have to fill up a little sooner, but that's generally not a bad thing - having at least a little gas in your tank is good for avoiding condensation in the winter, and being prepared for an unexpected disaster at any time.

 

Nope, it doesn't. I just tested it. You have to press "Trip" to see it.

 

Thanks for the input. I think I'll relax a little about the missing 2-3 gallons and focus more on enjoying the 9 or 10.

Now that I have filled up several (6) times, here's what I find: Total miles for the 6 fill-ups divided by gallons used = 45.9 mpg. And from adding the 6 tank display mpg and dividing by 6 = 47.6 mpg. Looks like 3.7 percent higher numbers (as others report) on the display. While the difference between calculated and display was as high as 11% on an individual tank, it averaged out to 3.7 percent difference with the 6 tanks.

Of course I don't know what is really the true gas mileage for these 6 fill-ups because of the differences in how full the pumps go till that first shut-off, slope, temp and what not (for 1st and 6th fill-ups), right? I'm wondering if the display will be more consistent, even though a little optimistic. By calculating based on miles driven/gallons pumped I think I will get more variation, sometimes a higher than true and sometimes lower. Seems to me like my best guess on my true gas mileage will be display x .965, or something like that. Sound about right from what others are seeing?

 

What was the lesson learned? How the fuel display works, or to read the manual.
SAMSUNG-SGH-I317 ? 2

 

i think you're right on. 6 tanks should be enough to give you a pretty close average, no matter where the pump stops.