Difference between actual and reported panel consumption

oh dear

 

They’re trying to broaden your horizons .

I work with a couple of Brazilians and columbians and when they get going, I just sit back and watch.

It gets loud and animated.

 

The fuel guess o meter is tough to use as a measure.

There are a lot of factors that can explain the variance between the display and reality .

I don’t pay it much mind personally as I am getting better mpg than 95% or more of the cars around me.

Good luck and keep us posted .

 

Yes, definitely the cause of the error was your "random" fills. The km/l, l/100km or MPG reading is really messed up when it's only partly filled. I've had 4 cars with dashboard displays - and while they're never 100% accurate, they'll all mess up if they're not filled.

Sometimes a faulty fuel pump/bowser which cuts off early will give a false reading. I can't find where I read it, but the DTE assumes you're filling the tank - not filling causes it to guess!!!

Oh - and if filled, is quite accurate - relatively.

 

Just keep at it, and try to keep your fill up technique consistent. But regardless, after 3 or 4 tanks, an overall calculation will be getting more and more accurate.

FWIW, my 3rd dash vs calculated is arou 7.5% difference, with what is it now, 160+ full ups.

 

how many km on her?

have you been tracking fuel economy since you got it?

did you buy it new?

did you fill to one click each time?

20% is a big discrepancy, but as stated above, there are variables that must be excluded when measuring.

 

The tank is now full, and the trip reads as 0 km driven at this point. The 43 L that you pumped shouldn't be taken in consideration because that was pumped to get you to full so you can calculate how many kms were driven per liter of fuel, which is how almost everybody calculates fuel economy. Miles per gallon for us Americans.

Assuming you filled her up until it clicked:

400 / 9.5 = 42.1 km / L

Second fillup on the trip, again assuming you filled her up till it clicked:

393 / 4.5 = 87.3 km / L

That's a huge difference between the two fillups.

But yeah, something wrong with the numbers, and I think it has to do with how you tried to calculate fuel economy. You tried to calculate it for the entire tank and not the distance you travelled, also taking into consideration how much fuel is left as well as DTE.

How much fuel left and DTE are just guesses by the computer, albeit how much fuel left is a bit more accurate than DTE, which is highly inaccurate and should only be used when you are really pushing the car to empty.

do not know if you left some numbers out, or remembered the numbers wrong, but I would discard these numbers and wait till another trip to figure your fuel economy.

 

I like measuring distance traveled using the odometer. When you fill up (always using the same technique), reset a trip meter (your preference, but always the same one) AND note the odometer reading, say on the gas receipt.

The next time you fill up, again note the odometer reading, and the trip meter (just for a cross-check), on the gas receipt.

Sure you can use the trip meters. I do, but mainly for feedback, and the cross-check. They are easy to accidently reset, or just lose track of. The odometer is permanent.

Subract the earlier odometer reading from the last reading: that is your distance travelled. Check that number against the trip meter. Then:

To determine kilometer per liter:

Divide kilometers traveled by liters of gas

Or, to determine liters per 100 kms (the usual in Canada):

Multiply liters of gas by 100, and divide by kilometers traveled.

The above is the mechanism of a ratio equation. For example, with 400 kms traveled and 20 liters consumed:



Results in fuel consumption of 5 liters per 100 kilometer.

 

and do it every time you fill up.

sounds like you're doing pretty well to me

 

Yeah, usually almost all of us who keep track of fuel economy will only do FULL fill-ups as that is easier to calculate. What kind of terrain are you driving though? Even roadways? Hills? Mountains? That will have a major effect on fuel economy as well.

If you find yourself a bit of ways away from home or from a gas station, all you need to do is slow down. The Prius gets phenomenal fuel economy when you are driving slow.

 

Refer to my POST #6.

The "DISTANCE TO EMPTY" (DTE) doesn't work well (or at all) except with completely filling the tank. I understand you might have not wanted to fill - maybe more expensive? - but the DTE can't help with that. Yes, sometimes it'll advance it a bit, but that's only from detecting some change in the Fuel Tank reading, but a wild guess only.

I can't see how TOYOTA does it - but VOLVO says "This calculation is based off of the average fuel consumption over the past 20 miles of driving along with the amount of fuel left in the tank."

Consequently, if your driving environment is variable, the DTE will vary considerably - I've seen it go up at times after a long stretch where the fuel economy is very good. A stretch of driving where the engine is working hard will see it plummet after driving like that for a while. Where it was particularly noticeable is over a mountain range - going up, DTE dropped quite a bit - but going down the other side saw it continue to drop - I assume because it's reading distance and assuming I'm still driving hard - but after a few kms downhill, it levelled out, barely moving.

 

I keep a spreadsheet which calculates l/100km (and UK MPG).


If you want the formulas I used - bearing in mind that they're for litres/100km (and UK MPG):

 

I've had fuel records since 1975 - spreadsheet since 1993. There are 2 other similar parts of the spreadsheet which document "Capital Purchases & Standing Charges" and "Service and other running charges". They are compiled together at the top.

 

So, all this talk and no info on how much difference between BC and actual consumption. On Gen3 there was 6-8% error, is Gen4 more accurate?

 

It's about the same - my last 3 cars and ones in my work fleet are similar - and all read slightly optimistically, which probably ties in with the need to keep some fuel in reserve so it isn't EMPTY when it reads EMPTY. The method of calculation takes readings from various sensors - and can't possibly be accurate - but it gives a good guide. I'd far rather it being a few percent out than running out of fuel the moment the needle hit "E".

As I said above, "VOLVO says "This calculation is based off of the average fuel consumption over the past 20 miles of driving along with the amount of fuel left in the tank."

SUBARU's manual (Forester) states "...shows only an approximate indication of fuel efficiency ... The driving range on the remaining fuel is only a guide."

RAV4 says "Use the displayed fuel consumption as a reference only"

FORD says: