mbedit Posted March 19, 2013 Report Share Posted March 19, 2013 So when I fill up, it seems like there is always a 1/2 gallon short. For example I just filled up today, and it was 12 gal I paid for at the pump, however, the trip meter says I only used 11.5 gal of gas. I've been keeping track and this is pretty consistent for every fuel up. Does the tank just not report 1/2 a gal on the top? It does affect the milage... for that 12 gal, the trip status says I went 483 miles and achieved 42 MPG, but really it was only 40 MPG. Has anyone else seen this? Is this something Ford can fix? JAZ 1 Quote Link to comment Share on other sites More sharing options...
plus 3 golfer Posted March 19, 2013 Report Share Posted March 19, 2013 (edited) Typically, the power control unit uses injection duration, injection rates and so forth to calculate the quantity of fuel injected. The injection quantities are accumuated. So, now the PCM can calculate instantaneous mpg, trip mpg, ect. and gallons used. In some cars like my 2009 TDI, I could adjust the calculation in 1% increments with a diagnostic tool to get a more accurate result. Because this calculation is not 100% accurate, the best way to get your FE is to keep track of the gallons you put in your tank and then divide such gallons into the miles traveled between fill ups. I don't know whether this can be adjusted on the C-Max by the dealer via their diagnostic tool. Edited March 19, 2013 by Plus 3 Golfer Quote Link to comment Share on other sites More sharing options...
wab Posted March 20, 2013 Report Share Posted March 20, 2013 So when I fill up, it seems like there is always a 1/2 gallon short. For example I just filled up today, and it was 12 gal I paid for at the pump, however, the trip meter says I only used 11.5 gal of gas. I've been keeping track and this is pretty consistent for every fuel up. Does the tank just not report 1/2 a gal on the top? It does affect the milage... for that 12 gal, the trip status says I went 483 miles and achieved 42 MPG, but really it was only 40 MPG. Has anyone else seen this? Is this something Ford can fix? YEP They all do it and I do mean ALL.Our last few cars have reported MPG incorrectly, some of them were Fords. Quote Link to comment Share on other sites More sharing options...
DaveofDurham Posted March 20, 2013 Report Share Posted March 20, 2013 Maybe the C-Max drafting behind you was pulling so hard that it drafted 1/2 gallon out of your tank. RachelnLa and Adair 2 Quote Link to comment Share on other sites More sharing options...
mbedit Posted March 20, 2013 Author Report Share Posted March 20, 2013 lol! it must be a stealth c-max behind me! Quote Link to comment Share on other sites More sharing options...
DaveofDurham Posted March 20, 2013 Report Share Posted March 20, 2013 lol! it must be a stealth c-max behind me! mbedit - I didn't realize you were the originator of this thread. I need to cover my tracks by saying that my C-Max has not yet been to Wilmington or any other Coastal NC location, no further east than Kinston and Greenville. Quote Link to comment Share on other sites More sharing options...
mbedit Posted March 20, 2013 Author Report Share Posted March 20, 2013 ;)I haven't been to RD with my new one yet... but may be passing through on Sunday! Quote Link to comment Share on other sites More sharing options...
DaveofDurham Posted March 21, 2013 Report Share Posted March 21, 2013 According to the odometer and lifetime mpg on our SEL, we have used 112.5 gallons of gas. According to our fill-up records we have pumped 112.1 gallons and the car says we have used 4.4 gallons since our last fill-up which totals 116.5 gallons - so our fill-ups are about 4% more than our usage recorded by our car or on average about 0.4 gallons difference on a 10 gallon fill-up. Quote Link to comment Share on other sites More sharing options...
mrobinso8 Posted March 21, 2013 Report Share Posted March 21, 2013 That is probably done by Ford so that the car gauge shows a better mileage number than you actually are getting. Keeps the majority of the people who do not check manually happy. My 2013 Fusion constantly reads 2 mpg higher on the gauge than calculated. The same is true for my traded in 2011 Fusion gas only vehicle. My 2006 Honda Accord was spot on comparing car to human calculations. That and the junk navigation system often makes me regret buying this car. If the car got close to advertised mileage they would not have to fudge the mileage calculations. Quote Link to comment Share on other sites More sharing options...
wab Posted March 21, 2013 Report Share Posted March 21, 2013 That is probably done by Ford so that the car gauge shows a better mileage number than you actually are getting. Keeps the majority of the people who do not check manually happy. My 2013 Fusion constantly reads 2 mpg higher on the gauge than calculated. The same is true for my traded in 2011 Fusion gas only vehicle. My 2006 Honda Accord was spot on comparing car to human calculations. That and the junk navigation system often makes me regret buying this car. If the car got close to advertised mileage they would not have to fudge the mileage calculations. " My 2006 Honda Accord was spot"It's sad that it takes losing a "class action lawsuit to FORCE a co. to do the right thing. Quote Link to comment Share on other sites More sharing options...
mbedit Posted March 23, 2013 Author Report Share Posted March 23, 2013 (edited) yeah... I had a 2003 Nissan 350z and it was dead on. Of course the window lift motor failed all the time on that one. Edited March 23, 2013 by mbedit Quote Link to comment Share on other sites More sharing options...
Jbtbga Posted March 23, 2013 Report Share Posted March 23, 2013 Great information on this thread. Will start to test my mileage manually on this tank. Has anyone seen the message going around Facebook supposedly from someone who works at a fuel wholesaler. He or she maintains that temperature of the ground tank, speed of the fill, and how much fuel is in the tank when you fill up all affect the actual amount of gas you get and, in the latter factor, use from your fill-up? I wonder if this is true and if so how much of a factor it could play in mileage. Quote Link to comment Share on other sites More sharing options...
StoBro2 Posted March 23, 2013 Report Share Posted March 23, 2013 My most recent fill-up calculated out to 38.2 MPG while my Trip 1 display showed 39.4 MPG. So it's about 97% accurate. I didn't check the computer's estimate of gallons consumed vs. what I was actually able to get into the tank. I think variations in the sensitivity of the automatic shutoff devices will always make the numbers different. Quote Link to comment Share on other sites More sharing options...
JAZ Posted March 24, 2013 Report Share Posted March 24, 2013 There will be differences in reported fuel delivery/consumption based on temperatures: http://www.ehow.com/facts_5522133_effect-fuel-temperature-mileage.html Quote Link to comment Share on other sites More sharing options...
Jbtbga Posted March 24, 2013 Report Share Posted March 24, 2013 My most recent fill-up calculated out to 38.2 MPG while my Trip 1 display showed 39.4 MPG. So it's about 97% accurate. I didn't check the computer's estimate of gallons consumed vs. what I was actually able to get into the tank. I think variations in the sensitivity of the automatic shutoff devices will always make the numbers different. I am going to try using the same pump for a while to minimize that factor. Maybe just a bit compulsive Quote Link to comment Share on other sites More sharing options...
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