Number of miles possible after fuel gauge hits zero?

It is very bad for your $3000 battery to run out of gas, it is very bad for your $600 fuel pump to run out of gas, it can be bad for your $1500 engine to run out of gas, you may need a tow to the dealer if you run out of gas, ($500) you will need to carry 3 gallons of gas back to your car before attempting to start it if you run out of gas.

If only there was a DTE meter, a gas gauge, and a low fuel light to warn you when you were about to be out.

 

There are a couple of threads with DTE and fuel light etc.
At this post (bullet points 4 and 5), I write about my findings about it, noting down DTE and actual refuelling. DTE is really all over the place...

 

We have had a Prius4 for around 5 months, after a 2 and a 3. Recently the fuel gauge has shown empty with 2 or 3 miles to empty. The tank has taken 36 litres max although it supposed to be a 43 litre tank. It looks like a faulty fuel gauge to me and the dealer hasn't much idea what the trouble is, but suggested that it might the odd 7 litres might be a reserve. Something I've never heard before, a "secret fuel reserve ! Has anyone else had this problem ?

 

No gas gauge show E just when you run out of gas, the owners would be all on the side of the road angry. Gen 2 was close, I ran out only 7 miles after the low fuel warning.

In the wake of the Gen 2, Toyota got very conservative, 8 liters in Gen 3. Fewer Gen 3 owners complained they were stranded.

 

Read just the first posting of this too-long thread:

[WARNING] Running out of gas | PriusChat

Then remember that your 'v' has lower MPG than the Liftback Bob used for that test. And that MPG varies with conditions, and gauging varies from car to car, so if you fail, you can't say that you were not warned.

You are reading more into that display than it is intended for. It is just a forecast, based on the assumption that the next miles ahead will have the same MPG as the recent miles behind. But that is almost never true, because MPG varies wildly depending on conditions, traffic, speed, temperature, precipitation, road surface conditions, elevation change, driver style, stop-and-go vs steady speed, etc.

If the forecast could be truly accurate, then it could be set to read '0 miles' at about the same mile that you really run dry. But because that level of forecasting is impossible, the car doesn't even try. Instead, there is some safety margin built it. It is up to you to not overrun that margin.

 

Drivers beware. The first car that I personally owned, ran out of gas with the gauge needle still above E.

Three cars later, I had one with more than 5 gallons remaining when the needle was on E

That wide gauging spread is why I now test the lower reaches of the fuel gauges on my cars. And I do that testing at a time and place of my choosing and convenience, not when circumstances demand a certain result in order to avoid major 'inconvenience'.

 

Don't be an idiot and drive extra just to save $.70. I never understood why anyone wants to squeeze that last mile out of a tank.

 

Yes, most cars I've had won't take the full tank quantity. Partly because they're protecting you from running out.

Use the TRIP button on the steering wheel and you'll find a DTE readout. It's reasonably accurate if you fill the tank each time - if you just put a bit it at times, it gets confused.

And there is a LOW FUEL warning comes on the dash about 60km DTE.

I can vouch for the FUEL PUMP issue - after my daughter ran out of petrol, though not on a PRIUS. Cost me a new fuel pump, a tow, 2 days without a car and the cost of a flush of the fuel lines - (it was an older car).

 

When it gets to zero miles remaining, fill it up, calculate how many gallons you had left in the tank (tank capacity - gallons put in), calculate the mpg (miles travelled since last fill divided by gallons put in), multiply the number of gallons you had remaining by the mpg and that will tell you how many miles you had left. Bearing in mind the mpg could be less if you do short/cold journeys with the remaining fuel, to err on the safe side use the minimum mpg you ever had out of the car when multiplying by the fuel remaining. I'd go on 40mpg (UK gallons) as a very conservative estimate and the least amount of fuel remaining in my tank on filling up at zero miles left was 7 litres (1.54 UK gallons) so 1.54 x 40 = 61 miles left at least. You could double that on a warm day with a warm engine in quiet traffic conditions.

 

OTOH, Bob Wilson ran his Gen1 and Gen3 Prii completely out of fuel more than 50 times, for engineering curiosity and testing purposes, many of them involving fuel comparisons that required one fuel to be removed before a different fuel was put in.

He never had a fuel pump failure. Nor needed a tow.

 

Bob is very careful not to keep driving. If you stop instantly, you won't harm the battery either, but it happens because owners do not stop instantly. Bob carries fuel with him so he does not attempt to make it to the next station, which is how most owners damage parts.

 

... which is also how I've done my tests. And on the non-hybrids, there is no chance of getting it to the next station.

I.e. it isn't the running out of fuel that is the problem. It is the operator errors on already-empty cars that cause the damage.

 

But the OP is not planning on carrying extra fuel on a closed course, as Bob does, so he WILL damage his car if he runs out. There is no point in it, but it is his plan.

 

I heard myself that there is 7 Litres of fuel left when the dashes come up DTE=0, thats approx 1.85 US gallons but in my own research, I found that I mostly have about 1.5 gallons left considering the 11.3 Gallon fuel tank.

 

My concern is that if the fuel gauge really is set to show empty when there are 7 or so litres in the tank then we are carrying that much fuel (weighing around 15 UK pounds) round which is effectively useless as once the indication gets to show empty then we have to fill up, or risk running out of fuel at some some time. Surely it is far better that the fuel gauge is accurate so that we can make up our own mind about how low we let it go.

 

Many of us technically minded owners would agree with you. But the Customer Service folks who must deal with the ID-ten-T service calls would have a greatly different viewpoint.

 

Sounds like some interesting calculations going on. I guess I'm turning into a boring old man. I just fill up when convenient when it gets to one dot.

A gauge that shows empty when the tank is actually empty is a ridiculously crazy thought. When that actually happens, I'm going to be first in line to open a tow truck company as that would become the new way to immediate wealth.

 

Just be within ~10 miles (EV only range at slow speeds) of a pit stop.

No, I have not purposely tried this, but did run through the chime only to see the last gas pip disappear in stop-and-go traffic, then chose to go nearly ten miles (mostly) on EV to a filling station.