how much fuel to keep in tank?

It also strains the oil supply. At least part of the problem in the 70's with gas shortages was brought on by people panicking and filling their tanks when half full, thus increasing demand by 50% overnight.

 

That would give a short term spike, but within a few days it would stabilize. Is the oil supply that sensitive where it can't handle a little ripple? [/rhetorical]

 

Would it? Try a simulation. Take a 20M barrel a day habit. 20Mb used every day, 20Mb produced/imported every day. Now increase ONE! day to 30 Mb. You are now 10Mb in debt. Call it, 1/4 of the stations are empty. How many days before it stabilizes (you can't increase production). That doesn't even include any new panic. You can solve it in one day if you can convince people there is no problem, but how would you do that?

 

Day 1: 30Mb demand
Day 2: 10Mb demand [since everyone fueled up the previous day, this days' demand is way down]
Day 3: 20MB demand, back to normal.

 

I tend to refuel towards the end of any weekend when the gauge has dropped to 1/3 remaining, or less. My main motivation: I'm trying to keep a running record of fuel consumption, and I don't 100% trust anyone else in my family to get it right. The few times someone else did put gas in that was the case, for one reason or another.

For insurance I only rely on the odometer to determine distance between fillups, as opposed to the tripmeter: too easy to inadvertantly reset it.

Besides my calculation issues: I just don't see the logic in chasing long tankfuls, and the potential risks.

 

Nope. 20 Mb is USED each day. Except now people are keeping their tanks 3/4 full on average rather than 1/2 full. That means 1/4 * average tank size * number of cars, has basically stuck into reserves. The 20Mb are still being USED (burned). Until you convince people to release those reserves, the 'crisis' continues.

There is a real situation that we are trying to model here. If your model doesn't match what really happened, you need an explanation, like for instance, that you did something to fix it.

 

Getting back to the subject title on this thread (not a snark)... I have taken to refueling when I'm down only 2-3 bars simply because I am impatient to report at Fuelly. Other than me "wasting" my time, is there any other practical reason I should wait until the tank is nearly empty before filling up? Simplified, am I hurting the car in any way by filling up more frequently?

 

Absolutely no harm done except your gas filler door will wear out a bit before mine Just kidding.

2-3 bars is a practical refill time for a person that doesn't want to keep close track of when/where they are going to refill next.

 

Just to be clear, not 2-3 bars REMAINING, but only 2-3 bars down from full.

 

I have.
Here's the deal:
I've heard this debate a few times in these hallowed halls, and I'll stipulate that the fuel pump is (A) in the fuel tank and (B) it uses fuel for some or all of its cooling and (C) some cooling is required. I have to stipulate this because everybody always SAYS these things, but I never SEE any documentation.
What I've never heard is how much fuel is required to submerge the pump and/or provide adequate cooling for the pump. A cup? A gallon? A quart?
How big physically is the pump? How much cooling is required?
How many Prius fuel pumps get burned out by moronic hypermilers trying to get into the 800-mile club?
You KNOW that there are folks that are trying to brag about how many miles that they get for every tank!!! How many of them are buying fuel pumps?
Thousands?
Hundreds?
ANY?


I have 35,000 miles in type.
"My" Prius (a company provided--2010 G3) is always filled at DTE + about 40-50. That means:

DTE - 20......the Prius says "Beeeeeep!" (IIRC)
I look at the Trip B display, which tells me how many miles have been consumed on this fuel load, and the (*ahem!!*) MDF's "guess" at my tank MPG/miles driven/ave speed.
I subtract 2-3 MPG from the MDF's SWAG, and multiply by 10. That provides a good estimation of how many miles I have to go before I get to the 10-gallon point.
I fuel up before then.
According to the manufacturer....this gives me a 1.something GALLON reserve.
In other words....I almost NEVER fill before the warning beep, and I usually wait well past DTE=0 before I load fuel.
Usually?
I load almost exactly 10 gallons.
I don't worry about the fuel pump cooling for two reasons:
1. It's not my car.
2. If 1.9 gallons isn't enough to cool the pump, I didn't cause a problem....I detected a problem.

There's a famous story (probably apocryphal) where General George S Patton rebuffed a senior colonel wanting to do a further detailed feasibility before taking action on a river crossing by stating: "We will cross where I made the mark!"
When asked "How can you be sure, General?" by the colonel, he stated:
"Take a look at my pants! That’s how shallow the water is! I walked across without collecting any enemy fire!"

That's how deep the river is here.
Of course...if you're one of these survival nuts, or there's a storm brewing in the Atlantic, or you're one of those nut jobs that believe that there's an increased likelihood of a major terror event on certain days (11 SEP, for example!) then it's probably not a bad idea to load fuel before you're at the BINGO point however (comma!) fuel pump cooling?
---Really?

 

The pump is full of gasoline as long as it is pumping gasoline and the gasoline flows right through the pump's electric motor so there isn't much to worry about unless you keep the pump running after it starts sucking air. Since it isn't your car, there is even less to worry about.

 

How I see it... most privately owned Australian Prii are - like mine - going to be fuelled at whatever interval the oil companies have currently decided for us irrespective of distance travelled and until quite recently that interval was weekly. If there was some major issue with this approach, people here probably would have discovered it by now.

The only issue I see is that the smaller fuel up amounts make average consumption calculations more prone to be influenced by the sensitivity of the auto-shutoff feature of the filling nozzle, though this will average itself out over the long term.

 

My brother has gone thru 2 fuel pumps in 2 years in a gm car. I attribute this to being a broke student who never runs the car on anything but empty.

You probably won't have a sudden catastrophic failure but your MTBF is going to suffer greatly as operating temps rise. Electronics will last orders of magnitude longer if kept significantly cooler. That being said it is probable that even in the worst circumstances the fuel pump is statistically likely to outlive the car.

Nexus 7 ? HD

 

My what is going to suffer greatly? MTBF?

 

MTBF = Mean time between failures, and it's a term that is often used in statistical gymnastics.

You have a C-type, so the fuel tank is a little different than the G3's tank, but let's be clear on this. You're not going to hurt your car if you fill it up consistently when there are any bars at all illuminated on your fuel gauge---presuming that the gage is accurate.

If you put a half gallon in every day on your way to work (when you're grabbing coffee and a doughnut, let's say...) it's not going to hurt your car any more than consistently waiting until the very last bar is illuminated before you load fuel each and every tank. Just don't overfill your tank. Stop at the first click and you'll be fine.

The only reason I wait 50 miles after the stupid fuel gauge says that I'm "empty" in order to load fuel is that I like to pump as close to 10 gallons exactly as I can, which simplifies my fuel efficiency guesstimation.
NOTE! This is on a G3, with an 11.9 gallon tank.
I don't have any stick time in a C-type, but I'll betcha that if you drive until DTE=0 (which on my car is twenty miles after you hear the warning "beeeep!") your fuel pump is still completely submerged in gas, and as another poster excellently pointed out....the fuel inside the pump does most of the cooling.

You really do not have to worry about this!
Toyota has already done all of the worrying for you, otherwise why would their MDF (Multifunction Display) tell you that the car is empty when there is still almost two gallons of fuel remaining in a G3???

Either Toyota is completely inept at making fuel gauges, or they're trying so hard to make this a non-issue that it keep cropping up as a very confusing issue to people who are trying to figure out why their tank ranges are so very short for a car that allegedly gets 40-50 something miles to the gallon. (My current tank is closer to 56.)

I've been on this forum for a couple of years, and there are a LOT of folks who like to strech their tank averages into the 600-700 mile range. There are even some 800 milers.
I haven't seen or heard of anybody replacing a fuel pump on any Prius. If you call your 5 closest Toyota dealerships and ask them if they stock fuel pumps for Priuses, I'll betcha they don't.
They don't need to.

Statistically?
I could be the NEXT POTUS!
I mean...hey...there are only 300 million citizens, and not all of them are eligible to vote, and only half of eligible voters ever bother!

People buy lottery tickets because it gives them a "statistical" chance of winning a few megabucks....so yes. "Statistically" your chances of replacing a fuel pump might be higher if you fill your car every morning or you wait until DTE=0...but here's something that's not so statistical:

Life is pretty short.
Don't sweat the fuel pump thing.

 

Statistically, I'd rather not walk after running out of gas. 2 pips is the norm for this guy.

Suspenders/belt. Primary/backup. Don't walk/Walk.

 

I do the same. Open to hear the theories. When the gas light blinks your down about 75% of a full tank. The blinking light comes on is when I fill up and takes 9 gallons on a 12 gallon tank. Also I use Fuelly so like to get to the blink and beep stage unless I'm traveling in an unfamiliar area.

 

LOL!

 

my dad always told me to keep at least a half a tank of gas ...me being a kid i never asked why i just always have...

 

My dad is not good with math puzzles, optimizations, or shopping by price. When bringing me a big load of stuff years ago, he refueled his truck at the highest price convenience store just before reaching my house, before learning that over here, different places charge very different prices. He was shocked at how much less I paid at a different station while we ran errands that evening.

Between gasbuddy.com, a more detailed understanding of my vehicle's fuel range, and a brain that actually enjoys math and puzzles and optimization planning, I keep my fuel bill significantly lower than with the old rule of reflexively filling up when the gauge reaches a certain point.

And yes, in certain foul weather conditions, I do maintain a much higher minimum. But the bulk of my travel is not in those conditions.