draperfish

My 2018 was doing the same thing, it was the battery, had a bad cell.

I'm on a road trip from Arkansas to Florida, my 2018 CC Z71 with 6.2 and 3.23 gears and BFG KO2 275/60r20 tires averaged 20.2 mpg over 1050 miles (computer was showing 21.5). I'm running 93 octane and cruise was set between 70 and 75 for most of the trip. Odometer was around 5,500 miles when I left, around 6,800 right now. I'm gonna check the mileage on the way back too.

I feel your pain, I just bought a 2018 GMC Sierra with the 6.2, my truck history is as follows: 1991 Ford Ranger bought new (leaking oil pan, tachometer quit working, started having electrical problems, less than 30K miles when I traded it), 1994 Toyota pickup with 4 banger, no issues, traded it with around 24K miles, 1996 Silverado 1500 5.0 bought with 24K miles on it (leaking rear axle seal around 55K) traded it with less than 60K miles, 1999 GMC Sierra bought new (at 12K miles failed cam roller bearing replaced under warranty) had almost 300K hard miles on it when it gave up the ghost), 2003 GMC Sierra 5.3 bought new, air conditioner never got super cold but never any major mechanical issues, got rid of it at 200K miles, 2006 Toyota Tundra with 4.8L bought new , still being driven with over 200K miles on it, 2007 Toyota Tundra with 5.7 bought used with 20K miles, no major mechanical problems with over 200K miles on it. 2010 Toyota Tundra with 5.7 bought new, no major mechanical problems, got totaled recently with 175K miles on it. 2014 Ram 1500 with 5.7 bought new (MDS lifters and cam replaced at 75K miles, fuel pump replaced at 105K miles), still in service at 120K miles. Toyota has been the most reliable trouble free trucks but the interiors aren't as nice as the GMC's and RAM. I'm not a fan of the AFM (Ram MDS) especially after the lifer failure on my RAM at 75K, but half the guys at work drive GMC and the other half drive RAM and we haven't had any lifter failures on the GMC's yet (one blown engine on a Yukon XL Denali with the 6.2 at 95K, but the guy who drives it changes the oil every 12K and drives 90mph everywhere so I think that was a factor), most of the RAMs have had lifter issues so I figured I'd give GMC another try. Can't bring myself to pay the extra premium for a Ford, my SLT that had all the same features as a Lariat was $10K less than the Lariat and $3K less than an XLT that seemed like a strip down model compared to the Sierra SLT.