BCM average fuel mileage

baddog2010 · February 15, 2019

Is there a way to 'recalibrate' the Average Fuel setting on 2018 Silverado ?
I am aware of the 'reset/clear' option on the dash display for the 'Instant Best mpg display'. Resetting has no effect. When I calculate fuel mileage manually its always 1.5 - 2.5 mpg less than the BCM display. Its been like this since day 1. Had 7 miles when purchased. Current mileage 35??. Assume should be past break in learn period time. I do same fill to neck each time, I dont round gallons. BCM claims 15.5-18 mpg avg, I get 15-16.5 manual. Same 25-30 mile drive daily. Did a 380 mile, 70-80 mph run and vehicle stated 20.1 mpg, manual 17.8. Have not done another long mile run.

SS502 · February 16, 2019

33 minutes ago, baddog2010 said:

Is there a way to 'recalibrate' the Average Fuel setting on 2018 Silverado ?
I am aware of the 'reset/clear' option on the dash display for the 'Instant Best mpg display'. Resetting has no effect. When I calculate fuel mileage manually its always 1.5 - 2.5 mpg less than the BCM display. Its been like this since day 1. Had 7 miles when purchased. Current mileage 35??. Assume should be past break in learn period time. I do same fill to neck each time, I dont round gallons. BCM claims 15.5-18 mpg avg, I get 15-16.5 manual. Same 25-30 mile drive daily. Did a 380 mile, 70-80 mph run and vehicle stated 20.1 mpg, manual 17.8. Have not done another long mile run.

I honestly don’t know but I don’t think so...I never use that view, I do what you’re doing and go the manual math way...I have my Yaw, Pitch and drive status showing full time.

Edited February 16, 2019 by SS502

redwngr · February 16, 2019

Factory tires?

6_2LTZ · February 16, 2019

Mine is off by 10% all day every day. Nothing you can do.

baddog2010 · February 16, 2019

Factory tires 265x75?x18, Somebody mentioned speedo is off, I have a Diablo tuner thought might try jacking with tire size, yet speedo appears proper, relative to other drivers. Dont have a speed, radar check around here, other than those I dont want to be checked by. have to do mile minute check on highway

Darmichar · February 17, 2019

On 2/15/2019 at 8:15 PM, baddog2010 said:

Factory tires 265x75?x18, Somebody mentioned speedo is off, I have a Diablo tuner thought might try jacking with tire size, yet speedo appears proper, relative to other drivers. Dont have a speed, radar check around here, other than those I dont want to be checked by. have to do mile minute check on highway

Get a GPS speedometer app for your phone.

SS502 · February 17, 2019

3 minutes ago, Darmichar said:

Get a GPS speedometer app for your phone.

Best answer given

Darmichar · February 17, 2019

4 minutes ago, Darmichar said:

Get a GPS speedometer app for your phone.

That said, my 2014 with 3.08 gears was about .5 MPG off all the time when I calculated manually. My 2018 with 3.23 gears is ALWAYS 1.5-2 MPG off when calculated manually. I have used a GPS app to check my speed and it is spot on.

baddog2010 · February 17, 2019

3 hours ago, Darmichar said:

That said, my 2014 with 3.08 gears was about .5 MPG off all the time when I calculated manually. My 2018 with 3.23 gears is ALWAYS 1.5-2 MPG off when calculated manually. I have used a GPS app to check my speed and it is spot on.

GPS vs Vehicle are same..... any other ideas why manual MPG is off ?

Sounds like the VolksVagon scam?!?

Edited February 17, 2019 by baddog2010
add on

Darmichar · February 17, 2019

1 minute ago, baddog2010 said:

GPS vs Vehicle are same..... any other ideas why manual MPG is off ?

I truly don't know. I drove over the road for 13+ years in Semi's that could track MPG to the +/- .1. It baffles me why these trucks are so horrible at doing the same.

I've seen others post here in other threads that there is a baseline map that isn't compensated for the different gear-sets they install in these trucks. Based on what I've seen owning two of them, I believe there has to be some truth to that.

baddog2010 · February 17, 2019

I had a '16 Impala that was always off 1.5-2 MPG manual check vs BCM. Figuered it was just a fluke, but now same on my '18 Silverado and hearing lots of other people have same issue.

baddog2010 · February 17, 2019

Found some information.

https://www.edmunds.com/fuel-economy/your-fuel-economy-gauge-is-fibbing.html

Seems to be a common issue among all manufacturers. Vehicle fuel economy gauge MPG reports a higher MPG than actual manual MPG calculations. Tweek the EPA requirements and to make the owners think their getting higher MPG than they really are. Gov Motors, Typical.

6_2LTZ · February 17, 2019

7 hours ago, baddog2010 said:

Found some information.

https://www.edmunds.com/fuel-economy/your-fuel-economy-gauge-is-fibbing.html

Seems to be a common issue among all manufacturers. Vehicle fuel economy gauge MPG reports a higher MPG than actual manual MPG calculations. Tweek the EPA requirements and to make the owners think their getting higher MPG than they really are. Gov Motors, Typical.

My 14 was bang on. Seems like 18's especially are off.

TJay74 · February 18, 2019

On 2/16/2019 at 11:38 PM, baddog2010 said:

GPS vs Vehicle are same..... any other ideas why manual MPG is off ?

Sounds like the VolksVagon scam?!?

There is no scam, the fuel mileage isnt even calculated by the BCM it is handled by the ECM and is a byproduct of the ECM calculating fuel used by the injector data of how much fuel it believes it has injected. It is only there as a tool and has never been accurate on any vehicle I have ever owned that provided that info. If you want accurate fuel mileage then you need to hand calculate it.