2021 Tahoe RST Abismal mileage

[revengejr]

Hi guys,
I bought a 21 Tahoe RST back in February. Before that I had an '18 Suburban and before that a '15 Tahoe. My wife likes a new truck every few years and drives primarily in suburbia as a school bus for our kids. Our driving habits have not changed however on this new Tahoe, we have been averaging about 8 mpg. It's advertised as 14 mpg city but were getting barely 1/2 of that. Anyone else experiencing a similar issue? We are at the pump almost weekly. It's a complete disappointment. I've had it in for servicing once under warranty already for an SRS light but they didn't note anything unusual. Any suggestions? Thanks for the help!

 

[1BADI5]

That 6.2 life YO!

 

[Goldenbear03]

That's extremely low and worth having looked into. My wife has somewhat of a lead foot and still managed mid-14's on her Escalade.

 

[MelloYello95]

A few months ago at the beginning of this chip shortage, I read several articles of GM leaving chips out of the fuel management system on the trucks. I hope they are not doing it with the SUVs. Would a company rightfully have to declare that to the consumer if that was the case? We have a 21 Yukon and averaged very well on our way home on the highways. Now that we've put about 2k miles on it around town, I'm averaging around 14-15mpg. That's about what my old one averaged. Make sure your not using anything below 87 octane.

 

[revengejr]

@1BADI5 It's a 5.3L not a 6.2. My suburban and older Tahoe had similar engines but we experienced much better mileage - about 15mpg. I don't think this truck has the AFM in it like older models. My old trucks would tell us when it was going from 8 cylinder to 4. I've also see the GM lawsuit about that issue on older models but from what I've read that only occurred after several thousand miles. This truck doesn't have that. We are at about 1,500 miles and about 160 hours on the engine. We keep in it in 2WD almost always and don't use any of the performance modes either. I've also noticed that cars computer reporting we are down to 50% of the oil life at only 1,500mi??? We are planning a 1,300 mi trip in June and will be towing about 4k lbs so I need to make sure everything is up to par. I will ask tomorrow about the AFM system. It's a good question.

 

[Goldenbear03]

I'm getting 16+ with my 5.3L AT4.

 

[Blueinterceptor]

That 6.2 life YO!

21 rst is 5.3. 6.2 only available on high country



what’s your highway mileage?

how much idling are you doing? That would impact your mileage.
If I sit idling(disable the auto stop) I get 9mpg

 

[Quark]

Having owned 2 other very similar models and assuming driving habits haven't changed it sure sounds like something is off . Hoping you get it resolved and let us know what was found.

I will bet that it will be a problem as it can be blamed on the owner and will be almost impossible to get their attention. If you need motivation to get this corrected remember GM's profit was $3 billion last quarter.

 

[revengejr]

Just got back from the dealer. The service advisor agreed that the mileage was low so they want to do a 1,000 mile test. Basically, come in, do an oil change, top off al fluids and then drive for 1,000 miles. Bring it back, they will check all of the levels, specifically the oil, and see if anything seems amiss. Then do it one more time at the next 1,000 miles and see if anything crops up. If nothing happens, then we concede terrible mileage. Not very promising especially since I am moving to Florida from NY in 5 weeks. They said this is a GM protocol and the dealer in FL should know what to do. Best part of it is we are driving from NY to FL, about 1,300 miles, so I can't even start the process until I get there, as GM requires it to be rechecked exactly at 1,000 miles. Yay! FML. I'll post on here in late June when the first 1,000 is done.

 

[JasonHTX]

Hi guys,
I bought a 21 Tahoe RST back in February. Before that I had an '18 Suburban and before that a '15 Tahoe. My wife likes a new truck every few years and drives primarily in suburbia as a school bus for our kids. Our driving habits have not changed however on this new Tahoe, we have been averaging about 8 mpg. It's advertised as 14 mpg city but were getting barely 1/2 of that. Anyone else experiencing a similar issue? We are at the pump almost weekly. It's a complete disappointment. I've had it in for servicing once under warranty already for an SRS light but they didn't note anything unusual. Any suggestions? Thanks for the help!

Yeah, you should have that looked at. I have a heavy foot and have not averaged below 13.5. That 13.5 was a week span where I was off work and running around inside town a lot.

Normal weeks ... 60% hwy 40% city with some idling mixed in, I get anywhere between 16-18mpg.

 

[Stbentoak]

Is there’s anything about the above 1k process that makes ANY sense? 1k miles means nothing to that engine and unless they do a detailed oil analysis both before and after on the same oil ( which prob won’t show anything abnormal..) that’s just kicking the can down the road.
It’s too bad that dealer service record is now on record, ( would hurt your trade in..) I prob would have talked to the GM of the dealership and had an discussion if they couldn’t bring the mpg’s up to normal soon, they would buyback on a friendly or unfriendly basis....Getting half mileage is an expensive proposition and not tolerable, and you are not getting what you paid for.....

 

[Blueinterceptor]

Zero out your avg mpg fuel usage. Reset the best to 25 miles. Go for a ride on a highway. Grand central parkway. At Night (less traffic)
25 miles each way. And see what you get. Little to no idling.

 

[Joseph Schroer]

Does the RST have a different gear ratio than your previous models? That would make a difference

 

[Mike Diaferio]

I have a 21 Yukon Denali with the 6.2 and average 16-18 mpg. My best is 21.4. I drive a lot of highway daily running normally around 75 mph.

 

[petethepug]

Reset milage computer while on the Highway. Rule out non city mpg in the equation.

Don’t dismiss the obvious the dealer should of checked like a hung up parking brake at the rear.


Sent from my iPhone using Tapatalk Pro

 

[adventurenali92]

@1BADI5 It's a 5.3L not a 6.2. My suburban and older Tahoe had similar engines but we experienced much better mileage - about 15mpg. I don't think this truck has the AFM in it like older models. My old trucks would tell us when it was going from 8 cylinder to 4. I've also see the GM lawsuit about that issue on older models but from what I've read that only occurred after several thousand miles. This truck doesn't have that. We are at about 1,500 miles and about 160 hours on the engine. We keep in it in 2WD almost always and don't use any of the performance modes either. I've also noticed that cars computer reporting we are down to 50% of the oil life at only 1,500mi??? We are planning a 1,300 mi trip in June and will be towing about 4k lbs so I need to make sure everything is up to par. I will ask tomorrow about the AFM system. It's a good question.

If I’m not mistaken all 5.3s in the pickups and SUVs from 2015- current have the active fuel management system. Though I think I heard with this latest generation GM is calling it dynamic fuel management now?

 

[jmm121783]

That is in no way normal. IDK about GM "leaving chips out of the fuel management system" that just sounds like FUD. I mean its not like they can not install a microchip, and the car functions as normal but with HALF the MPG.

I have had two 5.3s and I average with a mix of driving 18-22mpg.

Maybe you got some of the "winter mix" gas with higher ethonol which would reduce mileage but even than it shouldn't be that low. As other people have stated, the 1000mile thing from the dealer is absolutely POINTLESS and is just pushing off the problem 2000 miles down the road in helps it solves itself. I would not use that dealership anymore. Also if you still can't get a good answer I would contact GM customer service direct.

The only thing I could guess, if it was a mechanical issue would be a possible botched break-in? In which it should be burning oil, smoking and/or possibly leaking when parked. Either way, I run E85 in both of my cars, pretty much 75-100% of the time and I still get 14-16mpg in the PPV and almost 19mpg in the V.

 

[Quark]

That is in no way normal. IDK about GM "leaving chips out of the fuel management system" that just sounds like FUD. I mean its not like they can not install a microchip, and the car functions as normal but with HALF the MPG.

I have had two 5.3s and I average with a mix of driving 18-22mpg.

Maybe you got some of the "winter mix" gas with higher ethonol which would reduce mileage but even than it shouldn't be that low. As other people have stated, the 1000mile thing from the dealer is absolutely POINTLESS and is just pushing off the problem 2000 miles down the road in helps it solves itself. I would not use that dealership anymore. Also if you still can't get a good answer I would contact GM customer service direct.

The only thing I could guess, if it was a mechanical issue would be a possible botched break-in? In which it should be burning oil, smoking and/or possibly leaking when parked. Either way, I run E85 in both of my cars, pretty much 75-100% of the time and I still get 14-16mpg in the PPV and almost 19mpg in the V.

I agree it appears the dealer doesn't have the resources to properly diagnose this and is just kicking the can down the road. Hope a technician can chime in and describe the trouble shooting process to diagnose this so the owner can present it to the dealer. Dealers, they're the worst.

 

[revengejr]

Zero out your avg mpg fuel usage. Reset the best to 25 miles. Go for a ride on a highway. Grand central parkway. At Night (less traffic)
25 miles each way. And see what you get. Little to no idling.

Yeah, so my wife and I have been messing around with it and today we took a 10 mile trip on the Northern state toward Huntington and back (since you are clearly a fellow LI guy), computer calculated average MPG at nearly 11 mpg up from 9.8mpg just from about 20 minutes of highway driving. I think we figured out the issue. When my wife picks up the kids from school this year, she has to sit in a car line for up to 30 minutes and while the auto-shutoff kicks in for a while, since the A/C is running, the engine actually runs most of that time. So I think it's the idling that's killing the mpg. We have this 1,300 mile trip planned about a month from now and I am going to get the oil changed and everything topped up before then. We will see what 1,300 miles of I-95 driving does. I will report back my findings.

 

[revengejr]

Is there’s anything about the above 1k process that makes ANY sense? 1k miles means nothing to that engine and unless they do a detailed oil analysis both before and after on the same oil ( which prob won’t show anything abnormal..) that’s just kicking the can down the road.
It’s too bad that dealer service record is now on record, ( would hurt your trade in..) I prob would have talked to the GM of the dealership and had an discussion if they couldn’t bring the mpg’s up to normal soon, they would buyback on a friendly or unfriendly basis....Getting half mileage is an expensive proposition and not tolerable, and you are not getting what you paid for.....

Agreed and my wife and I feel the same. However, this is a lease but I like to keep my options open to potentially buy it out. I also think we figured out the main issue, lots and lots idling on my wifes part but her not telling me this until like this weekend. See my previous post. Thanks to everyone for all of the great ideas. I will report in about a month after we do a whole lot of highway driving and see what happens.