How to set fuel price

Sorry PriUncut, what you believe is not a credible fact that supports your position. All the current facts are disproving your position... but keep believing anyway... faith (belief) is a key component to all religions.

 

But I maintain that can't be accurate. How does the car know if I didn't keep topping it off... to the point of overflow (spilling out of the filler down the side of the car). Where is the sensor telling the car it's full?

I am just saying: it's a goofy feature. Maybe it's my first car and there is nothing to compare it to?

I'm still not convinced.

One thing I believe we all agree on... the manual is poorly worded. It does not explain that very well.

 

The car has computer controlled fuel injection and an odometer. It knows the exact distance travelled and the exact amount of fuel it injected into the engine. It doesn't care about tanks. You fill up from empty, half way, or top it off every 15 miles -- it just doesn't care. When the wheels are turning or the engine is burning gas, the computer is constantly computing its MPG. It keeps a history of these data points, maybe one every 30 seconds or every quarter mile (haven't cared enough to find out exactly). These data points are how it can build up the mpg, %EV, and other metrics by day, month, trip A&B, since start, and since last overall reset. The same data point may contribute to more than one of these stats.

Along with each data point, it probably stores the cost of the fuel used in that data point, based on the stored price per gallon that you entered. When you change the fuel price, you impact future data point computations but not the ones in the past. If you fail to enter the price routinely and accurately, that's your fault.

Now, the point where you can probably have a legitimate claim is that it doesn't do any cost averaging. If you fill up with $3 gas, burn a gallon, replace it with a single gallon at $2, and drive until empty then, assuming you entered the current price every time you added any gas, it will compute one gallon at $3 and the rest of the tank at $2/gal even though it should be the other way around based on what you paid.

That's part of what makes it an estimate. It's based on the assumption that you will generally refill at about the same point on the gauge and refill to about the same level. If you are in the habit of filling in awkward amounts because you came across a good gas price and decided to top off, or because you fill up $10 worth (however much that gets) when you have a spare bill in your wallet, then the estimate will be further off. Then again, unless gas prices change significantly from one fuelling to the next the difference is rather negligible.

It's not pretending to compute to NASA/ESA specifications of accuracy, and you shouldn't expect that. Just ignore the cost and savings screens if it bothers you that much.

Finally, if you overfill and let a half gallon run down the side of your car, that's wasteful and too bad for you. The car won't know and won't care because it's trying to measure what the car has done, not take responsibility for all actions done by you the human.

Honestly, it sounds like you don't want to be convinced. After this, I'm done trying on this topic.

 

Somebody explain this to me: How do you manually calculate your MPG (if you're writing it down in a book)... what information do you need to write down? And what information do you need to write down, if your calculating the cost of a trip?

I'm talking about the old fashion manual way... before computers in cars.

 

Manual:

• Col1: Date
• Col2: Odo
• Col3: Price
• Col4: Fuel Brand (optional)

Now get out a calculator and figure the delta in mileage and then divide that number the the gallons pumped.

Smart Phone (android) (my preferred) (other apps out there for ios too):

• Install free version of Fuel Buddy
• Enter beginning car info
• Click the red PLUS button
• Enter Odo
• Enter Quantity
• Enter full price, all digits
• Verify calculated cost
• Enter fuel source in Notes
• Save

It does the rest including a rolling average of various numbers.

My lifetime is current 54.5 mpg (low due to 800+ trip from Wa to Ca using cruise). It would be low to mid 60s without that trip. I'm still smiling as my previous averaged 45 mpg.

 

That's my point... you need to know the gallons pumped! I'm not trying to beat a dead house... BUT there is no way the Prius Accurately knows the gallons pumped... so the car has to estimate... unless the exact gallons are provided.

That was what I tried to wrap my head around.

Comparing to another car makes no sense.

We may never have an absolute explanation about Toyota's actual intended purpose of this function.

 

There are other ways to compute if you have the additional information that the engine ECU has. Since you don't, you mistakenly believe that the manual approach above is the only possible way to do the math.

 

Yup, the car knows how much fuel it is consuming, nuff said.

 

Interesting discussion. I can't imagine why anyone thought you'd want to compare your ongoing cost to drive this car with what your miles per gallon of another car was. That is not even the same thing! Cost/mile this car <> miles/gallon of another car.

What MIGHT makes some tiny tiny bit of sense (hold your breath for this one) is if I filled up on the way to work and did not have time to enter the cost right then. I race off to my meeting, driving 10 miles to work. After work, I remember I did not have time to enter the price/gallon so I do it then. But wait! What about that 10 miles I drove before I entered the gas purchase? Could that be what the mean by "comp". "Consumption" before I entered the price for the gas?

I do not know. At least that would make some sense. If I were doing this in a notebook with a #2 Ticonderoga, I would want to make that adjustment. When I entered the gas price for that purchase, I'd note the ODO miles and subtract 10 to push it back to what I should have let it do by itself.

In any case, thanks all, for the info on how to set the damn thing. You are right. Today, at almost 12K miles on the car, was the first time I saw the "enter fuel price?" message FLASH on the screen before a nerve impulse could even have gotten to the muscle in my hand. What kind of IDIOT set the time for that message at .25 seconds. Damn, talk about a human factors screw up.

 

I did the "comp" math for kicks and giggle before I bought my Prius... so I already knew my annual savings.

What sometimes makes comparative calculations more interesting is when the comp vehicle uses a different blend of gas. Prius uses reqular ($1.92 yesterday) while my former daily driver Acura CL uses premium ($2.39). There are some additional savings gained by using the cheaper gas too.... and then some more from the economy savings.

Thanks! The manual sucks when describing some of the menu settings and how to get to them...

 

If I wanted to track how much the car's costing me in gas, think I'd just put an extra column in my spreadsheet. I'm curious how they decide to include such features; I'm sure they're hoping it makes the car more attractive, helps sales.

Funny, I've never had much interest in toting up the $'s, prefer to track mpg, and do it myself.

 

I only used the A trip reset to zero when I put gas . The rest I check them once a month. I do like the difference set up that I can have . I think is cool.

Posted via the PriusChat mobile app.

 

This "quickly disappearing" setting mode was/is also a "feature" of the GIII. Took me a few months to figure out how to catch it in time. Does the GIV also give you a readout of cost of the trip when you shut down?

I do enter the cost of the fuel. I do, for smiles and giggles, watch for the cost of the trip.
I also -manually- record and compute mileage, with, OMG, a -pencil- and -paper-! How last century!
But it's more accurate.

 

I do the same - but with a spreadsheet column. The PRIUS readout assumes that both cars used the same fuel. Which isn't necessarily relevant. The PRIUS uses either E10 or unleaded, the #2 and #3 cars on my shortlist used Premium Unleaded and Diesel respectively - vastly different prices. I set the comparison car as a random similar sized 4 cyl car (ie Corolla).

 

What a valuable place for very useful information. I also had the price setting disappear before I could input the price. Thanks people!

 

It does not, at least the way it was setup when I bought mine, and I have not gone through all the various display options to see if it can be set up that way. Upon shutdown, my Gen 4 displays a "score" from 0 to 100 to give you an idea how efficient your trip was and it is broken down in three driving phases (acceleration, cruise and braking). It then gives suggestions as to how you can improve your score next time.

 

Mine in UK is the same, but it's just too much fluff for me to bother.

 

There is a screen that shows you how much money you've saved in fuel compared to another car, based on you inputting the cost of fuel per gallon and the mpg of the other car.

 

Ok, I'm just lazy enough not to care. But I do know I'm using half the petrol I was before the Prius came into my life.

 

Hi
Prius 2018, i’ve set gas price, but trip cost still show 0.0.

How many time to see amount?