Trip vs actual fuel use question

[Wnuk]

On my last fill up, the trip computer showed I used 11.6 gallons of fuel (see attached). The printed receipt showed I put 12.657 gallons back in. I can understand them being off a few tenths but not a whole gallon. 

 

Has anyone else encountered such a large discrepancy?

[kostby]

Yes. Car showed 12.74 consumed, pump dispensed 13.412 gallons.

I let it click-off automatically at around 13.0 gallons, and then pressed the handle once more until it clicked again.

I do that because when the station I regularly use is quite busy, the pressure change caused by others pumping from the same fuel selection can cause my pump to shut off quite prematurely, in some cases several gallons short of 'fill-up'.   And that's how you can get a calculated 35 miles per gallon from a 1996 Ford Taurus, one time. :yahoo:

 

Details are in Post #1027 in the '600 Mile' thread, just a few before your post today

http://fordcmaxhybridforum.com/topic/1025-600mile-cmax-club/?p=45605

 

I won't say that it's true for everyone but I'll venture a guess that the difference in our case is because we do LOTS of short trips less than 5 miles, many less than a mile.

Fairly often on short trips, the Trip fuel calculation shows 0.0 gallons used, but the Internal Combustion Engine definitely did come on briefly during the drive.  That, and doing the 'second click' on the pump.

Edited July 22, 2014 by kostby

[Marc Smith]

isn't gas tank only 12.9 gallons?

[kostby]

isn't gas tank only 12.9 gallons?

13.5 US gallons per 2013 C-MAX Hybrid specs in the 2013 Owner's Manual 3rd printing, page 353

14.0 US gallons for the 2013 C-MAX Energi Hybrid

Edited July 22, 2014 by kostby

[Wnuk]

Thanks for the info. I'll watch it and see what happens per tank. I do take some short trips but mostly travel 20 + miles each time out.

 

Had the car since June 30th and hit 2000 miles today :)

[PullingMussels]

This is interesting.  When I filled up yesterday, my 2014 C-Max reported using 11.32 gallons, but the pump give 11.123 gallons. 

 

This was only my second fill up, so I'll track it, for sure.  

[MichaelM]

This morning my fillup showed 11.73 gals. pumped to the second click off. The trip computer showed 11.38 gal used.

[C-MaxSea]

The rule of thumb for 2013ers has been that the pump will nearly always read higher (4,5,6, ? %).  We assume that the trip computer is off, but then again, not all pumps are the same, nor the angle the car sits at etc......  Ptjones tracks this well, and there are other threads discussing this as well.  I would sure like it to be more accurate, but don't know a thing about the details.  Throws a little caution into the 600 mile tank game - although the miles to empty is very conservative, and 'protects us' somewhat.  ;) ;) ;)

 

Michael, I'm guessing your 'fist click' reading may have been very close / more 'accurate'.  I would say anything within a tenth or two is a close/'accurate' reading.  And PM, yours was the reverse, most interesting if you were 'on the level' and pumping the same as your previous tank.  Yes, it will be necessary for a number of fill-ups to determine a trend for your vehicle.

 

Hmmmm, has there been an improvement in the 2014s???

 

Nick

 

Reminds me to look at our Member details to the left - it should identify the vehicle year, and yikes I need to fix mine !!!

Edited July 24, 2014 by C-MaxSea

[ptjones]

isn't gas tank only 12.9 gallons?

The Actual CMAX Hybrid tank size is 14gals which I have filled up to a few times. Pure Gas gives a more accurate reading. :)

 

Paul

[jdbob]

Hybrid tank is 13.5 gallons.

Energi tank is 14.0 gallons.

[ptjones]

Hybrid tank is 13.5 gallons.

Energi tank is 14.0 gallons.

Those are the numbers in the Owners Handbook, not the actual which you find out from running out of gas a couple of times. LOL :)

 

Paul

[rjam]

Hi all

Does anyone know why the average mpg in "my view" is different from average mpg in "trip1"? Seems they should be the same.

Sure there is a simple reason. I reset trip 1 with every fill up. 2013 Cmax SEL

[BIG ROCCO]

Hi all

Does anyone know why the average mpg in "my view" is different from average mpg in "trip1"? Seems they should be the same.

Sure there is a simple reason. I reset trip 1 with every fill up. 2013 Cmax SEL

Do you also reset the "my view" mileage?

 

I typically leave that one alone for several tanks, to get a more long term average.  That gives me 3 averages, all usually different - lifetime (currently 45.6 MPG BTW), trip 1, and my view

[rjam]

Hi

No. I just started to use my view so the temp guage would show.

[JAZ]

My View and the Trip 1/2 screens have separate resets.

[Tomasz Karwowski]

Today - 17.7l,(5,5l/100km)but I put 18,8l (5,9l/100km). 

[SnowStorm]

FWIW, I recently was looking at some old data (2013) for fill-ups where I compared "car gallons" versus "pump gallons".  The average error for 37 fill-ups had the car reporting 0.40 gallons low.  The histogram data for (car minus pump) was:

 

 3    -1 or more

 2    -1 to -0.75

11  -0.75 to -0.5

 8    -0.5 to -0.25

 9    -0.25 to 0

 2    0 to +0.25

 2    +0.25 to +0.5

 

Data from 14 recent fill-ups shows the car reporting 0.66 gallons low on average.

[radiobrown]

i have seen form .5 to 1.0 gal more pumped than used from the car.

in my BMW I can set the fuel usage and calibrate the MPG gauge in set increments, as cars will vary.

I wonder if there is software to access the OBC and make corrections (this would require several fillups at the same pump) and each time a change would need to be make to correct the issue for the car. this would however be each car would have to be done so I would guess the OBC uses Air temp, engine speed, Maf input, injector cycle (the way my BMW does it) plus engine load. at this rate the car will show on avg about 1 to 2 MPG increase due to the less fuel used and I wonder if it was done that way for a reason.

.5 to 1 gal is a fair amount of fuel to not be accounted for
for me today I had 350miles on the tank (cold weather and lots of heat being used the last week )
I pumped 12.1 so that avg rounding up to 29MPG

car displays that I used 11.3 that avg to 31

 

so is that how ford got the magic 41MPG for energy? I think yes
 

[ptjones]

Actually they got the numbers from the Fusion Hybrid/NRG and they used Ethanol Free gas.  If you check your odometer with GPS you see you actually went around 1.018% farther so that makes up some of the discrepancy. Interesting thing I have seen is the better your MPG's, the closer the actual gallons and Smart Gauge readings are. 

How do you get 29 mpg with an NRG, are you pluging it in? :headscratch:

 

Paul

[raadsel]

Actually they got the numbers from the Fusion Hybrid/NRG and they used Ethanol Free gas.  If you check your odometer with GPS you see you actually went around 1.018% farther so that makes up some of the discrepancy. Interesting thing I have seen is the better your MPG's, the closer the actual gallons and Smart Gauge readings are. 

How do you get 29 mpg with an NRG, are you pluging it in? :headscratch:

 

Paul

 

My guess would be never charging it and taking lots of short trips. Short trips and no added charge to the battery, with the heat blasting, would cause the car never to go into EV mode. At that point it is just a gas car carrying around an extra 500 lbs of weight.