Any way to adjust MPG calculation/display?

[WS6FirebirdTA00]

I tried to search without a lot of luck, maybe because there is nothing you can do.

 

My MPG on the dash has been consistently off 1.8-2.2 MPG vs actual calculated numbers. I filled up today and it showed 19.9 MPG on the display (reset every fill up) and calculated out to 17.7 MPG using the same pump and same fill process.

 

In my old BMW I could go in the computer setting through the dash to calibrate. Wondering if I or the dealer may have access to do the same. Being off that much makes it pretty much useless.

 

I am not sure if the range keeps some fuel in reserve for the calculation, but that seems to be 100% right adding that to my current mileage and dividing out.

[MaverickZ71]

Not unless something has changed with the newer generations.  My Driver Info Center fuel gallons used, average mpg, and instant mpg have always been overoptimistic by at least 8-10%.  And when my fuel gauge shows exactly 1/2 empty, it takes 11 gallons to fill instead of the 13 gallons it should be.  I asked my dealer to fix or recalibrate under warranty, and was told that's the way it is, there is nothing they could do.  I wonder if the factory calibration was for 3.08 gears and they were too cheap and lazy to recalibrate for the optional 3.42 gears.  

[WS6FirebirdTA00]

I figured that much. For something so simple, I don’t get it.

 

Well, I do. They want people to talk about how they get better than the sticker said. For me, I just cuss them (and many others) for how useless that “feature” is.

Edited August 31, 2018 by ws6firebirdta00

[iPhonez71]

Recently I changed a fuel gauge sensor for 2008 Hyundai Santa Fe. Anyway, it is the first time I changed fuel gauge sensor. The reading from instrumental cluster that informs volume of an empty tank instead from the fuel gauge sensor. The sensor needs to be submerged like a floating arm in a toilet reservoir. It will stop reading when it is no longer submerged or pushed by any fluid. 

Fuel level is measured by pressure, and fuel remaining is measured by volume. They both should not be equal. Beside, sometime, it predicts and estimates based on an average fuel consumption over a period of time including traveling speed and factoring in road geometry GPS and amount of horse power to move a load in your pickup going up hill and around curves. 

Edited September 1, 2018 by iPhonez71

[Darmichar]

This is my tracked MPG from my 2014 LT.  The grey bars peeking above the white bars are what the DIC reported MPG for that tank was.  It was ALWAYS +1 to +2 off of actual.

 

*EDIT* I also no longer record the DIC MPG because I know it's completely whacked, I do still reset the trip odometer out of habit though.  It seems to be even farther off in my 2018 so far after just 3 tanks of gas.  My 2014 was a 3.08 rear, the 2018 is a 3.42.

Edited September 1, 2018 by Darmichar

[WS6FirebirdTA00]

Love the data!

 

Oddly enough I installed that Airaid intake tune earlier today after fillup and used about 2 gallons of gas. I was in and out of the throttle a lot tryingto get some logs to see how much it affected theMAF calibration. I reset the fuel trims as well.

 

13.2 on the DIC and 14.2 at the pump

 

I will see if it follows through to the next fillup. Has me wondering if the fuel trims are too far from zero if it throws off the calculation. My trims are pulling decent fuel, 5-10% through a wide range on the MAF. Would like to mess with the tune, but want to make sure I get past a comfortable spot in the warranty.

Edited September 1, 2018 by ws6firebirdta00

[Darmichar]

11 hours ago, MaverickZ71 said:

 I wonder if the factory calibration was for 3.08 gears and they were too cheap and lazy to recalibrate for the optional 3.42 gears.  

I read this at lunch today and filled my tank after work and saw just how far off my DIC was on this new truck.  The more I thought about it, the more sense this sentence made.  I don't understand how the GM engineers can be as far off consistently as they are unless they just phoned this in and said "Ship it!".

 

My actual was 17.4, my DIC said 19.2

Edited September 1, 2018 by Darmichar

[aero10]

21 hours ago, MaverickZ71 said:

I wonder if the factory calibration was for 3.08 gears and they were too cheap and lazy to recalibrate for the optional 3.42 gears.  

I wouldn't think gearing would matter. I thought speed and mileage were calculated by wheel speed sensors. For the gearing to matter, they'd have to calculate mileage based on engine RPM, transmission gear, rear gearing, and tire size. Wheel speed sensor just needs tire size.

[Darmichar]

I figured they know approximately how much fuel is being used by the injectors at any given time and calculated it by taking that volume against miles driven.

4 hours ago, aero10 said:

I wouldn't think gearing would matter. I thought speed and mileage were calculated by wheel speed sensors. For the gearing to matter, they'd have to calculate mileage based on engine RPM, transmission gear, rear gearing, and tire size. Wheel speed sensor just needs tire size.

 

[WS6FirebirdTA00]

I thought the same. Seems pretty simple if it knows the pulse width and flow rate and all the offsets it should work well. It would be nice if it had an adaptive feature that monitored tank fillups to adjust.

[iPhonez71]

Regardless of what methods automakers are used to measure fuel, it is important we understand and prevent costly repairs. I mentioned earlier that I replaced 2 fuel sensors from 2008 Hyundai Santa Fe. I think eventually a fuel sensor will need to replace as it is ended its useful life. However, it will end sooner if it is not always submerged. When it is not submerged, the air temperature will contrast or expand the contacting point making it readings not accurate. This Hyundai had about over 25 fuel empty warning light on over the year. One has to use a gas container to fill it up. Now, I always fill up my 2014 Silverado and only experience 1 time this year that fuel warning light on. My advice is never to let your fuel gauge warning light on too often. Once in a while is probably okay. Word “too often” is subjective, so define however it describes your pickup.

[WS6FirebirdTA00]

I can count the times on one hand I ever let get go that low. Most of the time it was because I was pulling a gas tank.

 

I typically fill up around a half tank which is no more than once a week. Gas shortages about 10 years back got me in that habit too. If I am doing a lot of deiving I still don’t go below 1/4.

[iPhonez71]

16 minutes ago, ws6firebirdta00 said:

I can count the times on one hand I ever let get go that low. Most of the time it was because I was pulling a gas tank.

 

I typically fill up around a half tank which is no more than once a week. Gas shortages about 10 years back got me in that habit too. If I am doing a lot of deiving I still don’t go below 1/4.

You have a good habit, and good habit is hard to change. 

[aero10]

3 hours ago, Darmichar said:

I figured they know approximately how much fuel is being used by the injectors at any given time and calculated it by taking that volume against miles driven.

 

I thought they calculated fuel mileage based off the mass air flow sensor, hence why it's always so unreliable. It would make sense if they measured fuel, but I didn't think there was a fuel flow sensor.

[Darmichar]

24 minutes ago, aero10 said:

I thought they calculated fuel mileage based off the mass air flow sensor, hence why it's always so unreliable. It would make sense if they measured fuel, but I didn't think there was a fuel flow sensor.

I know diesel engines. The ECM on them has a fuel map that tells them where they need to be at any given RPM and load. Unless the injector is clogged, it should meter out that amount at that time. Keep track of that and you can measure fuel usage. 

 

I would assume they could do this with an injected gas engine too. I would agree the MAF works into the equation to keep the air/fuel ratio at ~14.2:1, but ultimately it's the injector and ECM that have to do the job.