Best year for GMC Yukon XL with 6.2L

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Looking at the 10th generation of GMC Yukon XL (Chevrolet Suburban). Thinking about 2012 or so. When did it get the 8-speed transmission?

I am mostly interested in the 6.2L engine as I hear it gets similar mileage to the 5.3L. I've had the 6.0L engine which got 11MPG consistently.
I now have the 2008 Tahoe with the 5.3L and the old 4L60E. I tuned the PCM myself in the Tahoe and the MPG came down a bit to 15MPG on the highway and worse in the city but the 5.3L got a considerable increase in power running 91 or 93 Octane.
I hear 6.2L should do at least as well as that and even higher with the 8-speed.

which years are best for the Yukon XL between 2007-2014? What gearing is available? 3.42? 3.73?

Second question, what's the largest gas tank one can install instead of the 31 gallon tank? Will the 2500-series Suburban 39 gallon tank fit?

I might tow occasionally but not enough to justify the 2500 series Suburban/GMC. (Not sure there was a 3/4-ton Yukon XL).
 
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I don’t think their 8 speed came out until 2014?? could be wrong, but yeah, I think it was 2014.
 
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Over 200,000 miles on my '07 Silverado HD with the 6 speed Hydramatic and 6.0L. Yes gas mileage sucks but I use it mainly for towing. Actually it gets pretty much the same mileage towing or empty. More gears mean more things to go wrong and more expensive to rebuild. The constant shifting can't be good for clutch life either.
 
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2007 and 2008 L92 6.2 is probably the most reliable paired with the 6L80E trans. No AFM and there were problematic first years of the 8 speed.

My 2008 AWD XL gets 12.5 mpg aroung town in hilly California, and I've seen 19 mpg on flat highway at 75mph. The final drive ratio is 3.42 and I'm running BFG AT K02 tires in stock size.
 

pacem

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Over 200,000 miles on my '07 Silverado HD with the 6 speed Hydramatic and 6.0L. Yes gas mileage sucks but I use it mainly for towing. Actually it gets pretty much the same mileage towing or empty. More gears mean more things to go wrong and more expensive to rebuild. The constant shifting can't be good for clutch life either.

I've had that exact same configuration. Mine was short bed 1500 HD, 6.0L. 26 gallon tank, 11MPG and always had to stop at a gas station. 6.0L needs at least a 40 gallon tank as it's almost as bad as Ford 460 or GM 454. I had a 460/7.5L, it got 11mpg no matter what you did with it. In 6.0L defense, it has almost as much power as these two.
I don't want 6.0L again.

Anyway, I am specifically inquiring about the 6.2L, seems only the Yukon XL (Suburban clone) has the option of 6.2...

I need some real life experiences with 6.2L mileage. If it can do about 15 MPG, I am happy.
 
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OK, what about the 2012-2013 Yukon XLs? Reliability-wise?
Not as good as the 07-08 because of the AFM/DOD system.

The only 2007-2014 Yukon Denali 6.2Ls that don't have the problematic AFM/DOD system are the 2007 and 2008. They have the 6 speed 6L80. Ours has 3.42 gears.

Today our 2007 Yukon Denali has183k miles. I purchased it 4 yrs ago w/130k. I run premium as recommended by GM. I get 19 mpg on long hwy trips and 16+ mpg locally (zero stop and go driving). I don't drive aggressively or tow. I love our Denali. It's a hwy wonderland.

They're not perfect. Example: In 2011 GM came out with a new improved driver side valve cover with a redesigned internal pvc system. GM issued TSB 10-06-01-008M: https://f01.justanswer.com/ebrock63...il+Consumption,+MIL+ON,+Engine+Runs+Rough.pdf

I could go on and on.
 

pacem

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2007 and 2008 L92 6.2 is probably the most reliable paired with the 6L80E trans. No AFM and there were problematic first years of the 8 speed.

My 2008 AWD XL gets 12.5 mpg aroung town in hilly California, and I've seen 19 mpg on flat highway at 75mph. The final drive ratio is 3.42 and I'm running BFG AT K02 tires in stock size.

AMF is not an issue, I can easily tune it out.
What about L92 vs L94?
 
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I don’t think their 8 speed came out until 2014?? could be wrong, but yeah, I think it was 2014.

Wiki says mid year 2015 bit of course they aren't necessarily the experts.

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AMF is not an issue, I can easily tune it out.
What about L92 vs L94?
You can tune it out, but the afm lifters are still in place. I have seen them rotate in the lifter tray and wipe the cam. If I had a L94, I would put the L92 cam in it with LS7 lifters.

My MPG above is also with power enrichment lowered to 65% throttle from 85%, and no delay, so it's power comes in sooner than the stock tune.
 

pacem

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Not as good as the 07-08 because of the AFM/DOD system.

The only 2007-2014 Yukon Denali 6.2Ls that don't have the problematic AFM/DOD system are the 2007 and 2008. They have the 6 speed 6L80. Ours has 3.42 gears.

Today our 2007 Yukon Denali has183k miles. I purchased it 4 yrs ago w/130k. I run premium as recommended by GM. I get 19 mpg on long hwy trips and 16+ mpg locally (zero stop and go driving). I don't drive aggressively or tow. I love our Denali. It's a hwy wonderland.

Yukon Denali is basically a Tahoe with better options/trip level. I am looking for a Burb-sized Yukon XL. More space and a bigger gas tank.
Still, 6.2L/6L80 and 3.42 and the MPG you get is very impressive.
I don't come anywhere near that with my present DD.
I got about 16 MPG with my 2008 Tahoe / 5.3L / 4L60 / 3.42 rear and after I tuned out AFM nonsense and added a performance tune to run on high octane only, it dropped to 15mpg. 5.3L was a slug from the factory and that really woke it up. I can only imagine blackbear tune is an even better choice.
It's good that the 6.2L requires high octane from the factory, meaning it has a higher compression.

I think 15+ MPG is very impressive for large SUVs.
 
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Here is some stuff from Wiki regarding the 6.2 that I gleaned out. There is the L-92, the L-86 /L-87, and LT-4. I’m on my 4th Suburban and have a 2008 3/4 ton with a 6.0 LY-6. In 2019 they switched from AFM in the L-86 to DFM in the L-87. Might be worth your while to go with the L-87. There is some detail on the L-92 becoming the L9H when flex fuel was added.

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pacem

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You are sure that 2007-2008 Yukon XL with the 6.2L did not have the AFM nonsense at all? That 2008 was the last year without it?
If so, that's good news and I can focus on these years. I don't mind 2008 at all.

My 2008 Tahoe with 5.3L has AFM, was drinking at least 1 qt of oil per 1000 miles.... after tuning it out, the problem disappeared. Just absurd that a company the size of GM can produce such shade - tree mechanic garbage. In fact when I got the car, checked the oil, none registered on the dipstick. Seems like one department designed the 5.3L engine, which is my fav V8 engine I've seen thus far adn then handed it off to another department which said how can we screw it up royally?
Now have 263K on my 5.3L engine with no issues. But the car is a beater, needs too much cosmetic work all around. And the miles are heading to 300K. Anything can fail on it at any time. Original tranny, original water pump and starter, etc.
Just time to let it go. I want the GMC Yukon XL.
 
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It's good that the 6.2L requires high octane from the factory, meaning it has a higher compression.
Premium is not "required", it's "recommended".
The first couple of yrs and 25k miles I ran mainly regular and mid-grade. Gas mileage suffered.
Again, I don't drive aggressively or tow.
 

pacem

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I will get a high compression tune then. I noticed that MPG actually improves with 91/93 Octane. You don't save anymore but come close to breaking even. Not to mention more obvious power.
Same thing with Ford V10 6.8L, by the way. Much happier with mid grade.
 
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