2021 Tahoe RST Abismal mileage

[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.


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[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.