DIC mpg varies a lot

Jkust

Original poster
Member
Dec 4, 2011
946
Hey all this has been bugging me for a while now. I commute daily with my 5.3 9-7 which is 96% highway with generally no braking at all once I get on the highway. What I can't seem to figure out is why the DIC average mgp varies depending on when I got gas. Generally the mpg is the best the day after I fill it up then normalizes as the tank gets used. After this last fill up I got 26.5 the whole way to work the first day and it droped each day until it settles down to 21 which is normal. The previous highest I ever got dic wise was around 22. I go to the same gas station every fill up, use the same grade and do 70 mph the whole highway route. When I first got the truck last November I manually calculated about three tanks which showed a best combined of 17.9mpg since even a little weekend driving and city driving drags the average way down. Of course a sustained 26.5mpg with an awd 5.3 isn't even possible and so there seems to be a few different things going on here. The air filter was new when I got the truck. What do you all think?
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
I would manually calculate a couple tanks now and see what you show.
 

Denali n DOO

Member
May 22, 2012
5,596
Jkust said:
Hey all this has been bugging me for a while now. I commute daily with my 5.3 9-7 which is 96% highway with generally no braking at all once I get on the highway. What I can't seem to figure out is why the DIC average mgp varies depending on when I got gas. Generally the mpg is the best the day after I fill it up then normalizes as the tank gets used. After this last fill up I got 26.5 the whole way to work the first day and it droped each day until it settles down to 21 which is normal. The previous highest I ever got dic wise was around 22. I go to the same gas station every fill up, use the same grade and do 70 mph the whole highway route. When I first got the truck last November I manually calculated about three tanks which showed a best combined of 17.9mpg since even a little weekend driving and city driving drags the average way down. Of course a sustained 26.5mpg with an awd 5.3 isn't even possible and so there seems to be a few different things going on here. The air filter was new when I got the truck. What do you all think?

I'm guessing you reset the DIC every time you fill up, it probably just averages out as more miles go on. If you reset the DIC each day before you go to work the readings will likely be around the same. Just a thought...
 

Jkust

Original poster
Member
Dec 4, 2011
946
Denali n DOO said:
I'm guessing you reset the DIC every time you fill up, it probably just averages out as more miles go on. If you reset the DIC each day before you go to work the readings will likely be around the same. Just a thought...

Sometimes I reset it for just highway mileage and sometimes I let it run for a whole tank. When I let it run, by the time it comes fill up time, the DIC is generally right on at 17.9mpgs or so on the whole tank. When I reset it as I enter the highway for the same trip, same driving habbits, it varies literally from 17 sometimes up to almost 27 on the twentyfive mile trip. Varying 10mpg is seemingly impossible but I see the pattern that the highest dic numbers happen right after a fill up. I can't help but wonder if my AWD is staying engaged or someother unseen issue however unrelated. I would have liked an instant mpg dic setting like the trucks and most other GM's I've owned have. My thinking is that if the overall average is pretty much spot on when it runs for a whole tank, how can it be so far off on any given trip if i'm resetting daily for that same trip. I mean if a v8 in a 5000lb truck was actually capable of 28mpg's...
 

million-miles

Member
Jan 10, 2012
189
You stop and fill up right by the interstate. Just saying. Then you hop on the interstate and your down hill just a little bit during your drive. You could be avg over 30 mpg but as soon as you go up hill or flat or get of the interstate the mpg is going to tank. Yes if you reset your dic after you fill up then its going to jump around like crazy.
 

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