Drop in mpg

L86 All Terrain · December 10, 2016

Does your area run winter gas? They just started switching a bit ago. Also could be your intake is starting to gum up if you dont run a catch can. Increased warm up/idle times etc.

Sean Neilan · December 10, 2016

I get the exact same mileage on 89 or 91/93 as I do on 87

redwngr · December 10, 2016

Add about 1 gallon of 121 octane to every third or fifth tank and you will be fine. I run premium in my truck year-round and my gas mileage never fluctuates

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But you're in Georgia.

Winter changes to fuel are regional.

michaelfloyd84 · December 10, 2016

Yes maybe so but we have winter fuel also

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Haus_Z71 · December 10, 2016

10 mpg is definitely rough. I appreciate all the input. My main thing is I just want to make sure there is nothing wrong with my truck. And I would like be to just know why and if upgrading the octane would do anything. If 93 would bring my mileage back up

I guess the obvious is probably already covered, but have you had your air filter replaced?

What did they do with your service? Just oil change? I would make sure they used 0W-20.. but a GM service department should know what your truck recommends.

These Direct Injection engines do have a lot of build up on the intake valves. I believe the dealers recommend this service at 30k miles, and it should improve fuel economy. HOWEVER, I am very skeptical of this service, because after I had it done, my cats failed from so much gunk being cleared out. Dealer had to replace the cats under warranty.

Edited December 11, 2016 by 2015_Sierra

dagwood2001 · December 11, 2016

I have also had issues with my gas mileage over the years. I had a 2014 for 2 years and am currently about a year and a half into a 2015. Both totally stock with the 5.3L V-8.

I don't drive all that much (don't know if that has any impact, my 2015 only has 6100 miles on it) and both trucks, amazingly, have averaged 13.4 MPG, exactly. I'm not thrilled with that but I really only need to fill it up every 10 days or so, and gas is hovering around $2-2.15/gallon (although with the Giant discount tied to grocery purchases I usually pay about .75 cents a gallon every third fill) so it really isn't the end of the world but I sure seem to get worse mileage than most?

I'm in Philly BTW where it either seems to be 100 or 25 degrees.....

Sean Neilan · December 11, 2016

I have also had issues with my gas mileage over the years. I had a 2014 for 2 years and am currently about a year and a half into a 2015. Both totally stock with the 5.3L V-8.

I don't drive all that much (don't know if that has any impact, my 2015 only has 6100 miles on it) and both trucks, amazingly, have averaged 13.4 MPG, exactly. I'm not thrilled with that but I really only need to fill it up every 10 days or so, and gas is hovering around $2-2.15/gallon (although with the Giant discount tied to grocery purchases I usually pay about .75 cents a gallon every third fill) so it really isn't the end of the world but I sure seem to get worse mileage than most?

I'm in Philly BTW where it either seems to be 100 or 25 degrees.....

If you're just driving around town especially in a congested area it'll be bad. I'm on Long Island and if I'm driving around town and no highway I'll get 12-14 depending on how many red lights I get stuck at.

66deadhead · December 11, 2016

Ok, I gotta comment on this cause I'm experiencing the same thing on my 2016 at 11,500 miles. It seems like since it's gotten colder out my gas mileage has took a dive, and it also seems to be running a little rougher at idle too.

I was averaging about 17-18 mpg back and forth to work, and now I'm getting about 14-15 mpg, I gas up at the same station for almost every fill, run medium grade, and it's a top tier fuel (Exxon) I been attributing some of this to using the remote start in the mornings. Can't explain the rougher idle though. I thought about shooting a can of seafoam or CRC intake/Throttle body cleaner in it , but am hesitant to do so as I don't want it to possibly throw a code. I did install a catch can recently, at about 11,000 miles. But the mileage was already dropping off before that. I spoke to the dealer and they recommended a upper induction cleaning and throttle body cleaning at about 37,000 miles. Yep... 37, 000 miles, 1000 miles after the factory warranty runs out. I found this hilarious, and cracked up right in their faces when they told me this. They also told me I really don't need a catch can on it, as the Silverados are not really prone to valve coking.... Yep, you heard that right... Yet at 37,000 they wanna do a upper induction cleaning. Lol. They did say the Chevy Traverse has a huge problem with intake crud though and attributed that to poor engine design. I am Not trying to turn this into a catch can thread, just stating where I'm at with this truck now, and am wondering the same thing about the gas mileage and why it's dropping off so quickly since it's gotten cold out. And At this point and time, I would have to agree that the colder weather definitely has something to do with mileage, and how the truck runs. But I am also wondering if it's partially because of any crud that may have built up in the engine already. ....or maybe it's a combination of the 2 ?? Guess one day it's warmer on a weekend, I'll get ballsy and shoot a can of cleaner through it and see what happens if it continues to plummet.

Eddie 70 · December 11, 2016

One thing I would do is check my oil level and make sure it is not over the top line on the dipstick. In fact GM recently backed off on 8.5 quarts of oil and dropped back to 8 which should probably be about halfway between low and full on the dipstick. Check your tire pressures and make sure they are at the recommended pressures at least or where you like to run them. I run mine at about 35 PSI. Check the air filter and see how it looks.

My 2014 has 70000 miles on it and I am currently averaging 23.XXX mpg for the last 27k miles. I bought the truck with 42k and that is when I started tracking it.

One thing I would do is check my oil level and make sure it is not over the top line on the dipstick. In fact GM recently backed off on 8.5 quarts of oil and dropped back to 8 which should probably be about halfway between low and full on the dipstick. Check your tire pressures and make sure they are at the recommended pressures at least or where you like to run them. I run mine at about 35 PSI. Check the air filter and see how it looks.

My 2014 has 70000 miles on it and I am currently averaging 23.XXX mpg for the last 27k miles. I bought the truck with 42k and that is when I started tracking it.

Boardmember · December 11, 2016

I assume or hope everyone is calculating this manually, not relying on the not-so-accurate DIC...

Eddie 70 · December 11, 2016

I assume or hope everyone is calculating this manually, not relying on the not-so-accurate DIC...

I use aCar app on my phone. Input the mileage and gallons added to the tank and it does the calculations for you. It's always about 1 - 1.5 MPG lower than the DIC.

Sean Neilan · December 11, 2016

I assume or hope everyone is calculating this manually, not relying on the not-so-accurate DIC...

I calculate mine manually every tank and it has been within +\- .1 of the DIC.

Sean Neilan · December 11, 2016

Ok, I gotta comment on this cause I'm experiencing the same thing on my 2016 at 11,500 miles. It seems like since it's gotten colder out my gas mileage has took a dive, and it also seems to be running a little rougher at idle too.

I was averaging about 17-18 mpg back and forth to work, and now I'm getting about 14-15 mpg, I gas up at the same station for almost every fill, run medium grade, and it's a top tier fuel (Exxon) I been attributing some of this to using the remote start in the mornings. Can't explain the rougher idle though. I thought about shooting a can of seafoam or CRC intake/Throttle body cleaner in it , but am hesitant to do so as I don't want it to possibly throw a code. I did install a catch can recently, at about 11,000 miles. But the mileage was already dropping off before that. I spoke to the dealer and they recommended a upper induction cleaning and throttle body cleaning at about 37,000 miles. Yep... 37, 000 miles, 1000 miles after the factory warranty runs out. I found this hilarious, and cracked up right in their faces when they told me this. They also told me I really don't need a catch can on it, as the Silverados are not really prone to valve coking.... Yep, you heard that right... Yet at 37,000 they wanna do a upper induction cleaning. Lol. They did say the Chevy Traverse has a huge problem with intake crud though and attributed that to poor engine design. I am Not trying to turn this into a catch can thread, just stating where I'm at with this truck now, and am wondering the same thing about the gas mileage and why it's dropping off so quickly since it's gotten cold out. And At this point and time, I would have to agree that the colder weather definitely has something to do with mileage, and how the truck runs. But I am also wondering if it's partially because of any crud that may have built up in the engine already. ....or maybe it's a combination of the 2 ?? Guess one day it's warmer on a weekend, I'll get ballsy and shoot a can of cleaner through it and see what happens if it continues to plummet.

As me and others have pointed out in here already these trucks seem very sensitive to cold and when the temp drops below 45ish there is a noticeable (and in some cases drastic) drop in mpg

MySilverado180 · December 11, 2016

Maybe my story will help. I have the 5.3 with 8 speed and I have a lifetime mpg of 18, and this includes some towing. I average 19-20 on my daily drive to work (mostly highway). It does go down some with the cold.

I use Oil Life Monitor (OLM) to know when to change my oil. Get it done just above 0%. I track my mpg very closely and started noticing the mpg would go way down towards the end of my oil life. This was only when I was using up the free oil changes the dealer gave me. I have since switched to doing oil changes myself, and I use Mobile 1 fully synthetic 0W-20. What a difference in mpg. There's no longer a dropoff in mpg toward the end of my oil life. Can't explain it, just my observation.

last truck · December 11, 2016

1st he DIC doesn't measure the amount of fuel flow, it measures miles to gauge readings so we all know the first 1/8 tank lasts longer than the middle 1/4 tank.. 2nd did this drop occur about the time the truck was leveled, lifted or new tires wee added?