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domerdel

17 MPG city driving (not 22) on 2021 Sierra 1500 AT4 diesel (3.0)

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Hi everyone,

 

I've put about 1400 miles on my new 2021 GMC Sierra 1500 Duramax Diesel with the goodyear wrangler tires and 18" wheels. Most of my daily commute is city driving where average speed gets to about 40-45 MPH. My average MPG has been around 17 MPG which is about 23% below the rating of 22 MPG. I make a conscious effort to be hyper aware of driving habits such as keeping RPM's low (not gunning it between gears or when stop lights turn green). My daily commute obviously isn't a flat perfect road, but I'm a bit skeptical that i'm 23% below the rating (i'd be much happier with a less or equal 10% variance). I live in California (northern), so environmental standards are pretty much overkill compared to other states, and making sure to read the label at the diesel gas pump.

 

What other factors should I consider to improve MPG?

 

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23 minutes ago, domerdel said:

Hi everyone,

 

I've put about 1400 miles on my new 2021 GMC Sierra 1500 Duramax Diesel with the goodyear wrangler tires and 18" wheels. Most of my daily commute is city driving where average speed gets to about 40-45 MPH. My average MPG has been around 17 MPG which is about 23% below the rating of 22 MPG. I make a conscious effort to be hyper aware of driving habits such as keeping RPM's low (not gunning it between gears or when stop lights turn green). My daily commute obviously isn't a flat perfect road, but I'm a bit skeptical that i'm 23% below the rating (i'd be much happier with a less or equal 10% variance). I live in California (northern), so environmental standards are pretty much overkill compared to other states, and making sure to read the label at the diesel gas pump.

 

What other factors should I consider to improve MPG?

 

Im averaging 19-20 right now during the winter in idaho. Warm up idle is really killing MPG and it being cold. I have a silverado with 2.5/2 lift and trailboss takeoffs, so pretty compareable. Id imagibe you will gain a little with more time to break in.

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20 minutes ago, domerdel said:

Hi everyone,

 

I've put about 1400 miles on my new 2021 GMC Sierra 1500 Duramax Diesel with the goodyear wrangler tires and 18" wheels. Most of my daily commute is city driving where average speed gets to about 40-45 MPH. My average MPG has been around 17 MPG which is about 23% below the rating of 22 MPG. I make a conscious effort to be hyper aware of driving habits such as keeping RPM's low (not gunning it between gears or when stop lights turn green). My daily commute obviously isn't a flat perfect road, but I'm a bit skeptical that i'm 23% below the rating (i'd be much happier with a less or equal 10% variance). I live in California (northern), so environmental standards are pretty much overkill compared to other states, and making sure to read the label at the diesel gas pump.

 

What other factors should I consider to improve MPG?

 

No you are most likely right in the spot within a mpg or so. The window sticker is obviously inflated showing optimal results which in the real world doesn't happen. You are around 3 mpg better than my 6.2 around the city which sounds about right for a diesel imo. 

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1 minute ago, BIGDOGx said:

No you are most likely right in the spot within a mpg or so. The window sticker is obviously inflated showing optimal results which in the real world doesn't happen. You are around 3 mpg better than my 6.2 around the city which sounds about right for a diesel imo. 

I realize window sticker isn't real world, but a 23% variance seems like a lot compared to the sticker. I do appreciate the comparison though; thank you for replying

4 minutes ago, ullose272 said:

Im averaging 19-20 right now during the winter in idaho. Warm up idle is really killing MPG and it being cold. I have a silverado with 2.5/2 lift and trailboss takeoffs, so pretty compareable. Id imagibe you will gain a little with more time to break in.

what's the optimal warm up engine temp so that I'm not over doing it? Mornings here are still around 40-45 degrees for another month

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Window stickers are inflated numbers. However, I bet your window sticker with larger wheel and tires is the same as my window sticker with smaller diameter tires from the factory. I would also bet that our gearing is the same.

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7 minutes ago, domerdel said:

I realize window sticker isn't real world, but a 23% variance seems like a lot compared to the sticker. I do appreciate the comparison though; thank you for replying

what's the optimal warm up engine temp so that I'm not over doing it? Mornings here are still around 40-45 degrees for another month

I just let it idle for 5-10 minutes usually, lets the seats an steering wheel warm up, the engine doesnt warm up much until you drive it. 

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1 minute ago, mjonesjr84 said:

Window stickers are inflated numbers. However, I bet your window sticker with larger wheel and tires is the same as my window sticker with smaller diameter tires from the factory. I would also bet that our gearing is the same.

Tires really arent bigger, just heavier

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Just now, ullose272 said:

Tires really arent bigger, just heavier

Still has the same effect. Added weight will lower mpg as well.

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2 minutes ago, mjonesjr84 said:

Window stickers are inflated numbers. However, I bet your window sticker with larger wheel and tires is the same as my window sticker with smaller diameter tires from the factory. I would also bet that our gearing is the same.

You have a solid point. larger wheels, tires with the 2" lift yet same rating as let's say the elevation 1500 w/ a Duramax package.

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4 minutes ago, ullose272 said:

I just let it idle for 5-10 minutes usually, lets the seats an steering wheel warm up, the engine doesnt warm up much until you drive it. 

that's about my idle time in the cold mornings as well.

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I'm getting the same 17-18mpg with town driving. 2 miles to work, 2 miles to the gym, 2 miles to work, 2 miles back home. Three stoplights in between each. 

 

I park my truck in a garage that stays 58* minimum so I'm not warming mine up. Start up and waiting on garage door to open, then away I go.

 

 

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As the window sticker always states, your results may vary.  

 

It sounds like your commute, not so much as your driving habits are causing your lower MPGs.  

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I have a ‘21 Sierra SLT with the 3.0. My work commute is only 7 miles each way, a lot of stop and go. Max speed 40mph. And I turn off auto stop. I average 21-22mpg for a full tank of gas. I ran a few tanks of gas with auto stop enabled and it was a 1.5-2mpg increase. 
 

highway driving: 30mpg if I go 65, 27ish at 70mph. 

 

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If you have winter blend fuel out there it will reduce your mpg also. Depending on how cold you get the louvers in front of your radiator will reduce it too, engine likes it warm and wants fuel.

 

-Grover67

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6 hours ago, Wormydog1724 said:

I'm getting the same 17-18mpg with town driving. 2 miles to work, 2 miles to the gym, 2 miles to work, 2 miles back home. Three stoplights in between each. 

 

I park my truck in a garage that stays 58* minimum so I'm not warming mine up. Start up and waiting on garage door to open, then away I go.

 

 

Here's a good example. Guys, most of the extra fuel used in the winter has to do with the viscosity of the oil which is HIGHLY effected by????????????........Temperature. Give this a look. Note the marked difference in viscosity between 0C (32 F) and 40C (104F) ? Below 0C it goes nearly vertical. Example is a 5W40. 

 

If you warm the motor for say 20 minutes that's 20 minutes of fuel used not moving an inch. Two miles to work wont get the oil to operating temperature even if you warmed if for 20 minutes. AS the 3.0 already used 0W20 the only thing you can do is add a pan heater. That should allow a measurable gain. 

 

Viscosity of Engine Oil – viscosity table and viscosity chart :: Anton Paar  Wiki

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