Kilgore Trout

Am I misreading your post? Did you say they have had since Monday and today "mentioned" lifters as a possible culprit? I mean, it should take a qualified tech about 20 mins to fully diagnose a collapsed DFM lifter.

A little late to the party, just saw this thread, sorry. The OP's mileage seems low to me. I own a 2021 Sierra 1500 AT4 6.2L with the optional Duratracs. I get about 13 around town (that is with almost zero highway miles). If I get even like a quarter of them highway miles, I can see over 16 on the averages pop up. If I stand on it stop sign to stop sign, I can definitely get sub 10 on the average, but that is driving like I am young enough to be worrying about acne.

Yeah, I actually can't say the decibels go up, maybe it is a frequency change thing. All I know is the bigger the blocks in the tread and the higher the load rating, the louder they seem to get as they wear. I too really like the tire (other than the noise). We go up on some pretty gnarly 4X tracks, this winter on some extremely icy and muddy trails and they seem to grip really well, better than I even hoped.

Pretty hard to attribute that issue to a failed DFM lifter. Given it wouldn't start after all the racket he described, I would suspect it was something a little more dramatic.

My AT4 came with Duratracs. I like the tire off road and seems to be doing well on the ice/snow we have had so far. They are freaking loud and as new as they are now, I know they will be REALLY loud at 20K miles. I am too cheap to replace them until they are worn out but definitely am not looking forward to the deafening din to come.

If Idle Hours are not included in Total Hours, somebody at GM is functionally illiterate.

My Sierra 6.2L 1/2 Ton AT4 is my third vehicle (least used). It has sat for a couple of weeks a couple of times since I bought it. It is pretty cold here as well, never failed to start. I would seek out a new dealer for maintenance.

I was referring to a link of a report of DFM lifter failures on the "non-DFM" engines.

I used a fish tape I had laying around and sent it up from the bottom the route I wanted it to follow, taped the cable run I wanted to pull back down to the end of the tape and pulled it through. You can buy them for under $10, it doesn't need to be super long.

I had intended to buy a Backflip MX, but found something a little less expensive and given its many good reviews, thought I would give it a shot. It took about 30 minutes to install and it keeps the weather out just fine, but clearly is not as nice looking as the BF MX. I have used my bed quite a bit since installing the Gator SFX and it is super simple to fold it up and roll it back out when I am done with hauling whatever. https://realtruck.com/p/gator-sfx-tri-fold-tonneau-cover/v/gmc/sierra-1500/2021/

Personally, if my dealer couldn't diagnose it, I would find another shop. Parasitic drain can be challenging to nail down, but a competent shop will find it.

Got a link to such a report? I have not seen any.

GM built some 21's without DFM (turned on), it was reportedly due to the chip shortage. Your Monroney window sticker calls it out.

Certainly couldn't hurt to take it to a trusted shop and have them check the alignment.

Totally agree.