2020 5.3L gas mileage

[ljramsey]

I have a 2020 Sierra 1500 SLT 5.3L and am disappointed with the highway gas mileage. With cruise control set at 72mph I am averaging just shy of 20mpg. What kind of gas mileage are others with the 2020 5.3L and 10 speed transmission seeing? Thank you.

[JimCost2014]

What kind of MPG were you expecting from a 5000 lb. truck going 72 MPH?

[CamGTP]

If your avg combined miles per gallon is nearly 20, you are doing pretty darn good for a full size truck. That means you are getting 23-24 on the freeway and 16ish in the city. That's almost exactly what the truck is rated for.

 

Drive 65 and the mileage per gallon should go up.

[ljramsey]

40 minutes ago, JimCost2014 said:

What kind of MPG were you expecting from a 5000 lb. truck going 72 MPH?

Well, I was averaging 23mpg with my 2019 5.3L with 8 speed transmission.

[JimCost2014]

5 minutes ago, ljramsey said:

Well, I was averaging 23mpg with my 2019 5.3L with 8 speed transmission.

Honestly with my 18, 6.2, 8 speed, can get close to 23 (what the trucks says), if I stay at/right under 70.

Once I exceed that MPH, it does start dropping quickly.

 

Seems like the new engines and the 10 speed should be getting more MPG's.

[TNTSierra]

My 2018 Sierra SLT 6.2L with 8 spd got 23 to 24 mpgs all day long running 70 mph. My new HC with 10 spd and 6.2L gets around 20 mpg.  I can’t come close to replicating those numbers. But this new truck drives, rides, shifts, and accelerates so much better than my 2018.  I’ll take the 2 to 3 mpg hit. That 1 to 2 “clunking” in 8 spd drove me nuts. 

 

My stepdad just got new Sierra with 5.3L and 10 spd and he is getting 22 to 23 mpg. He is really liking this new truck. He came from a Furd ecoboost that claimed to get 23 but could never crack 20 mpgs ever in the 5 years he owned it. 

[Imcrazy]

My 16 with 5.3/3.42/4x4 was lucky to get 20-22 at 70mph. Haven’t checked my 2020 8 speed, 3.23 4x4 5.3 yet. I’m surprised you saw those kinda numbers on your K2, what rear end gear did you have in it?


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[OnTheReel]

18 minutes ago, TNTSilverado said:

My 2018 Sierra SLT 6.2L with 8 spd got 23 to 24 mpgs all day long running 70 mph. My new HC with 10 spd and 6.2L gets around 20 mpg.  I can’t come close to replicating those numbers.

Yeah, my 19’s a pig compared to my 16. These new trucks are a lot bigger, so any benefit of the weight reduction and added gears is wiped out by the giant frontal area of these things. At least that’s what I think the difference maker is. I don’t really care though. Gas is cheap. For now.

 

Mine will do an honest 20 MPG at 70 with the 6.2/10/3.42s. Bump it to 80, and I’m lucky to see much over 18 unless we are on some flat ground. I would imagine the 5.3 should do a little better. Maybe it just needs to be broken in a bit more.

[TNTSierra]

23 minutes ago, Imcrazy said:

My 16 with 5.3/3.42/4x4 was lucky to get 20-22 at 70mph. Haven’t checked my 2020 8 speed, 3.23 4x4 5.3 yet. I’m surprised you saw those kinda numbers on your K2, what rear end gear did you have in it?


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My 2018 had 3.23 gears. And yes no one ever believed I got those numbers till I showed them on the instrument cluster and then also calculated it out after fill up. My nephew who is HUGE Furd guy always knocks GM vehicles till he rode in it and actually saw what I got. It shut him up real quick. 
After tuning it, I also achieved the same MPGs. Idk if I got a unicorn but if that truck wouldn’t have had the d@mn 8 spd clunking, I would have probably never gotten rid of it, or let’s just say not be tempted to test drive a new T1. But then again, this new 10 spd is so smooth and the added features along with extra space in Crew Cab for my kiddos and our 90 German Shepherd, makes up for the loss of mpgs

[TNTSierra]

Here is one time I took picture running 70 down highway for home to work. It’s a 32 mile flat stretch, but 450+ hp after tune was still pretty impressive. 

Edited November 27, 2020 by TNTSilverado

[Enough]

My 2018 Silverado LT had 3.42 gears, a six speed trans, and the same size tire as my 2020 Silverado LT with 3.23 gears and 8 speed trans. I run 75 on the highway.

 

The tires on the 2018 were Bridgestone Duelers and the 2020 has Genral Grabber AT's.  Both 255 17's.

 

Life time mileage on the 2018 was 22.5 at 38,000 miles before the electrical gremlins forced me out of it. At close to 8,000 miles lifetime on the 2020 is 20.1.

 

My opinion is that the engine in the 2020 is spinning just a tad under optimal RPM's at 75 with the 3.23's. Best 400 mile MPG average so far on the 2020 was 24.1 at 79 MPH. The stock General AT tires on the 2020 vs the Stock street tread on 2018 Bridgestone's probably factor into things too.

 

There is no comparison about how much smoother the 2018 ran than the 2020 does from 500 to 1,500 RPM's. The 2018 would idle at 500 RPM so smoothly and quietly it was amazing. I could stop to talk on the phone , put it in park, and when I got out of the truck 45 minutes later the tach and door chime would be the only indication the truck was still running. If the 2020 gets down to 500 RPM's the antenna looks like it's going to vibrate off.

 

If GM would have found the issue in a reasonable amount of time with my 2018 at 243 miles when it first happened, at 3,800 miles the second time it happened, or at 38,000 miles when it happened again I would still have it. Three strikes and it was out.

[TNTSierra]

I also had 285/45/22s on my truck. It came with stock 20s but I upgraded to 22s. Still never affected the gas mileage

 

There are days I miss it just a smidge! Lol

 

[J_Miester3]

2020 GMC Sierra SLT 5.3 10 speed. Almost 5300 miles average is 19.4 mpg so far. Stock rims and tires. 

[gregus73]

2020 Denali, 5.3 10 speed. Getting 23-25 mpg. All highway miles. For city driving, use my Wrangler JL and 2018 Trax.

[2016 Sierra Owner]

I average 16-17 all city driving as I live 7 miles from work. 20 5.3 10 which is pretty much exactly the same from my 16 5.3 6.