6.2 Engine - Octane Requirements?

Jordan18 · June 16, 2015

Not Sure what rear differential you had on your 2008, but the 6.2 only comes with the 3.23 gears. my 2014 is tuned I run 91 octane and have 3.42 gears in the rear. In town I get on average 15.8 mpg and highway is similar to what you are reporting.

Just food for thought.

Mike

If I can remember it was 3.42 in my 08'. My 15' comes with a 3.42 since it's NHT, with 8 speed. My limited understanding is it's equivalent to the 3.73 in the 6 speed because of it having more gears, and 3.23 8 speed is equivalent to the 3.42 in the 6 speed. I noticed the 8 speed greatly helps around town mileage so far, compared to my 08 at least. But honestly I really haven't tripped around town too much, if I had to guess it was anywhere from 15-17 mpg in the short times I did bomb around down one day.

My 08 did have slightly larger than factory tires, it was levelled, and I also ran a power programmer in it. It also had a bull bar on the front which would probably reduce the aerodynamics somewhat.

mzodarg · June 16, 2015

If I can remember it was 3.42 in my 08'. My 15' comes with a 3.42 since it's NHT, with 8 speed. My limited understanding is it's equivalent to the 3.73 in the 6 speed because of it having more gears, and 3.23 8 speed is equivalent to the 3.42 in the 6 speed. I noticed the 8 speed greatly helps around town mileage so far, compared to my 08 at least. But honestly I really haven't tripped around town too much, if I had to guess it was anywhere from 15-17 mpg in the short times I did bomb around down one day.

My 08 did have slightly larger than factory tires, it was levelled, and I also ran a power programmer in it. It also had a bull bar on the front which would probably reduce the aerodynamics somewhat.

You enlightened me. According to the Chevy website and every 6.2 I've seen, 3.23 is the only offering. I'm clueless to what NHT is? You mention that 3.23 with the 8 speed is equivalent to 3.42, I haven't seen that documentation (source).

I actually am not impressed with how my truck tows my 4500 # pontoon, I went to the dealer with boat in tow and test drove the 6.2 with my boat attached. IMHO it was worse than my tuned 5.3, that's why I started researching the differential choices and 3.23 was the only choice for the 6.2.

By no means am I questioning what you have said, I'm actually excited that there may be another option for me.

looking forward to your documented source so I can read up on it.

TIA,

Mike

Isriam · June 16, 2015

the 2014 6 speed denali 6.2 standard is 3.42. you have to get the 6.2 tuned. your 5.3 tuned is probably a better driving vehicle than a stock 6.2

redwngr · June 16, 2015

Edited to try and align columns:

Overall ratios:

Type: 8L90 eight-speed 6L80 six-speed

Gear ratios (:1) 3.23 3.42 3.42

First: 4.56 14.73 4.03 13.78

Second: 2.97 9.59 2.36 8.07

Third: 2.08 6.72 1.53 5.23

Fourth: 1.69 5.46 1.15 3.93

Fifth: 1.27 4.10 0.85 2.91

Sixth: 1.0 3.23 0.67 2.29

Seventh: 0.85 2.75 N/A N/A

Eighth 0.65 2.10 N/A N/A

Reverse: 3.82 12.34 3.06 10.47

The 8L90 has lower low and higher high ratio than the 6L80.

The same thing happens when the 8 speed NHT (w/3.42) is compared with the 6 speed NHT (w/3.73)

The transmission ratios can be verified here:

http://gmpowertrain.com/product_guide/REV2_2015_Information_Guide_121014.pdf

CptMcSaug · June 16, 2015

The 3.23 in the 8 speed is equal to a 3.66 in the 6 - speed when in fist gear. The 8 speed has a stupid low first gear.

From Higgs

"you can change rear end ratios and tire sizes with the current access. the only thing missing is pressure and shift speed alterations and detailed torque management changes. you can make more sweeping changes as it is now.

personally, I wouldn't change the rear ratio anyways. the 8 speed has a 4.56 first gear which is steep. 4.56 X 3.23 = 14.72 the 6L has a 4.02. 14.72/4.02 = 3.66 rear ratio equivalent (which is almost a 3.73). I don't think I would change it unless I went to 35's."

Jordan18 · June 16, 2015

You enlightened me. According to the Chevy website and every 6.2 I've seen, 3.23 is the only offering. I'm clueless to what NHT is? You mention that 3.23 with the 8 speed is equivalent to 3.42, I haven't seen that documentation (source).

I actually am not impressed with how my truck tows my 4500 # pontoon, I went to the dealer with boat in tow and test drove the 6.2 with my boat attached. IMHO it was worse than my tuned 5.3, that's why I started researching the differential choices and 3.23 was the only choice for the 6.2.

By no means am I questioning what you have said, I'm actually excited that there may be another option for me.

looking forward to your documented source so I can read up on it.

TIA,

Mike

The gents above were kind to provide the sources. "NHT" is basically GM's package code for the max trailering option on their trucks.

robvas · June 16, 2015

2014 you could get the 3.73 with the NHT with the 6-speed, in 2015 you can get a 3.42 with NHT in the 8 speed

mzodarg · June 16, 2015

Ok thanks for all the insight! One thing I just tried was to build a Denali and a high country, neither had an option for max trailing pkg and if I switched the rear end to a 3.42, it switched the engine to a 5.3.

What am missing?

Mike

cybeast · June 16, 2015

You can't get the max trailing pkg in the Denali just SLT

Jordan18 · June 16, 2015

Ok thanks for all the insight! One thing I just tried was to build a Denali and a high country, neither had an option for max trailing pkg and if I switched the rear end to a 3.42, it switched the engine to a 5.3.

What am missing?

Mike

Max trailering is not available to the high country or denali.

Jordan18 · June 16, 2015

Double post

Binobanbino · June 16, 2015

Getting back to the OP I only use 93. I cant tell if there is a differnce between 87 and 93 because I have never used 87.

mzodarg · June 17, 2015

Max trailering is not available to the high country or denali.

Appears to be the same for every model I'm trying to build. Just saying...

Jordan18 · June 17, 2015

Appears to be the same for every model I'm trying to build. Just saying...

So when you try to build one on the chevy site you can't get the max trailering for any trim? If I understand that correctly

I noticed when I went through their site for example, when you pick an LT, you have to select 20" wheels for the max trailering option to be selected. Bear in mind the 5.3L option will still be a 6 speed 3.73 rear end.

For the LTZ same thing, it wants you to pick 20" wheels if you get the max trailering. Their site has changed since I was last on it, I actually built one over the phone with a sales rep and picked exactly what I wanted and needed.

I contemplated a 5.3L SLE/SLT Max trailering with a 5.3L but wanted to try the 6.2L. Octane requirements were a factor at the time before I decided, so that is when I trialed my own truck with 91 for a few months and noticed marginal cost differences at the pump.

If you are looking for better towing and a 6.2L, I love mine. I have a 5000lb enclosed trailer my 08 struggled to pull well on straight roads, this new truck is able to accelerate up decent grades with it. Night and day.