5.3L vs 6.2L V8

[Hector Salamanca]

2 minutes ago, f8l vnm said:

Can someone show me where GM says 91+ is required for the 6.2 ? 

Recommended ? yes, if your in 100 degree doing back to back pulls , or your pulling a 8k+ trailer . but just dont see the need for higher octane for cool weather or basic street/highway driving. 

This is not an insult to anyone who does use 91+ , just my personal observations . 

It's on fueleconomy.gov 

I noticed it when I was researching trucks. They're most likely getting their information from the manufacturers, unless they made an error it clearly reads Premium. 

 

I'm sure that using 87 Octane in the 6.2 is fine. We have a car in the household that recommends 91 octane, been running 87 since we got it in 2012 and its totally fine. 

If the manufacturer recommends it, then there is a reason why. I'm no expert, but its probably going to result in slightly better performance. Why else would they recommend it? 

 

[Jav_eee]

Can someone show me where GM says 91+ is required for the 6.2 ? 
Recommended ? yes, if your in 100 degree doing back to back pulls , or your pulling a 8k+ trailer . but just dont see the need for higher octane for cool weather or basic street/highway driving. 
This is not an insult to anyone who does use 91+ , just my personal observations . 

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[Jonofmac]

   

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 It is NOT required as people seem to think. It's recommended (as your image shows) to achieve maximum power and fuel economy but runs just fine with regular (for those that say premium is required, read the text note. Says "fuel down to 87 may be used"). I'll post this extremely in depth ~70 page research paper from AAA conducting testing on multiple vehicles that recommend or require premium to see what the effects are. They actually say that they recommend running regular in the 6.2 because the mpg increase does not offset the fuel cost. They state that power reduction was ~2% or less on their dyno testing and fuel economy was most affected on flat ground. They observed 0 pinging or knock issues on regular because the ECU was able to switch to a lower octane table. Everyone saying the 6.2 requires premium is wrong. GM recommends premium. It was likely done to increase mpg number because they get dinged on fleet average mpg. So it's in their interest to tell us to use premium if it increases mpg 1-2 mpg, because their fleet average goes up, even though it's cheaper $/mi to run regular with slightly lower MPG. Their only metric is mpg for fleet average mpg.

 

There are NO issues with running regular gas in the 6.2, despite what ill-informed people seem to think and say with 0 data or facts. Yes, your mpg will be affected slightly. Yes, your power will be affected slightly. Data shows 0-13% reduction in MPG (depends on driving conditions as shown by my below link), and power is down ~1-2% at > 4k rpm (no change below 4k). If you don't rev your truck much, you don't even lose HP!

 

I'll post this research link again....

 

I personally run 93 in my 6.2, but gas is cheap. My old truck needed premium (heavily modified 2500) and got 10 mpg. So doubling my mpg is awesome for me anyway.

 

https://newsroom.aaa.com/wp-content/uploads/2017/12/Premium-Fuel-Phase-II-Research-Report-FINAL-2.pd

 

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[Glava2876]

13 minutes ago, Jonofmac said:

 

It is NOT required as people seem to think. It's recommended (as your image shows) to achieve maximum power and fuel economy but runs just fine with regular (for those that say premium is required, read the text note. Says "fuel down to 87 may be used"). I'll post this extremely in depth ~70 page research paper from AAA conducting testing on multiple vehicles that recommend or require premium to see what the effects are. They actually say that they recommend running regular in the 6.2 because the mpg increase does not offset the fuel cost. They state that power reduction was ~2% or less on their dyno testing and fuel economy was most affected on flat ground. They observed 0 pinging or knock issues on regular because the ECU was able to switch to a lower octane table. Everyone saying the 6.2 requires premium is wrong. GM recommends premium. It was likely done to increase mpg number because they get dinged on fleet average mpg. So it's in their interest to tell us to use premium if it increases mpg 1-2 mpg, because their fleet average goes up.

 

There are NO issues with running regular gas in the 6.2, despite what ill-informed people seem to think and say with 0 data or facts.

 

I'll post this research link again....

 

I personally run 93 in my 6.2, but gas is cheap. My old truck needed premium (heavily modified 2500) and got 10 mpg. So doubling my mpg is awesome for me anyway.

 

https://newsroom.aaa.com/wp-content/uploads/2017/12/Premium-Fuel-Phase-II-Research-Report-FINAL-2.pd

 

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I run 93 too to get the best performance -to me it would be like having someone give me a super model and saying we recommend real nice clothes, but you can get her stuff at Walmart if you want.

Thanks for clearing it up though, I thought that it was required too!

 

[Jav_eee]

 It is NOT required as people seem to think. It's recommended (as your image shows) to achieve maximum power and fuel economy but runs just fine with regular (for those that say premium is required, read the text note. Says "fuel down to 87 may be used"). I'll post this extremely in depth ~70 page research paper from AAA conducting testing on multiple vehicles that recommend or require premium to see what the effects are. They actually say that they recommend running regular in the 6.2 because the mpg increase does not offset the fuel cost. They state that power reduction was ~2% or less on their dyno testing and fuel economy was most affected on flat ground. They observed 0 pinging or knock issues on regular because the ECU was able to switch to a lower octane table. Everyone saying the 6.2 requires premium is wrong. GM recommends premium. It was likely done to increase mpg number because they get dinged on fleet average mpg. So it's in their interest to tell us to use premium if it increases mpg 1-2 mpg, because their fleet average goes up, even though it's cheaper $/mi to run regular with slightly lower MPG. Their only metric is mpg for fleet average mpg. 
There are NO issues with running regular gas in the 6.2, despite what ill-informed people seem to think and say with 0 data or facts. Yes, your mpg will be affected slightly. Yes, your power will be affected slightly. Data shows 0-13% reduction in MPG (depends on driving conditions as shown by my below link), and power is down ~1-2% at > 4k rpm (no change below 4k). If you don't rev your truck much, you don't even lose HP!
 
I'll post this research link again....
 
I personally run 93 in my 6.2, but gas is cheap. My old truck needed premium (heavily modified 2500) and got 10 mpg. So doubling my mpg is awesome for me anyway.
 
https://newsroom.aaa.com/wp-content/uploads/2017/12/Premium-Fuel-Phase-II-Research-Report-FINAL-2.pd
 
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That AAA study keeps being brought up but they tested the L86, not the current L87. I tried searching but can’t find any info on the technology change that might’ve happened. I’m not arguing 93 is required, I’m just saying that test, in this convo, means nothing.


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[Jonofmac]

That AAA study keeps being brought up but they tested the L86, not the current L87. I tried searching but can’t find any info on the technology change that might’ve happened. I’m not arguing 93 is required, I’m just saying that test, in this convo, means nothing.  

 

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I would argue that it still is quite relevant. 

The L86 vs L87 are virtually identical outside of DFM vs AFM from every piece of data I can find.

 

Same bore, stroke, compression ratio, HP and torque.

 

The introduction of the more advanced variant of AFM (which is DFM in 2019), won't affect any WOT measurements. The only thing it could affect is part throttle might see less of a difference than the AFM models.

DFM is an evolution of AFM, where the engine has 17 different modes instead of the 2 in AFM (V8 vs V4). DFM can run on a number of cylinders ranging from 2 to 8 cylinders instead of 4 or 8. It also rotates the combustion between used and unused cylinders to help with uneven wear. That was the only "significant" change of L86 to L87. I could find all this with a quick Google across a few different websites and looking at GM's tech specs.

 

The larger MPG drop of the AFM vehicles was due to the engine having to run in V8 mode more than it was with premium gas. DFM now allows you to run on modes between V4 and V8 modes. So perhaps a V6 mode would help decrease the gap between premium and regular gas mileage, further. This is only a hypothesis, but seeing as how AAA recorded V4 mide was activated less, it would seem possible that mpg could be improved if you could take advantage of a V6 mode instead of running V8 full time.

 

It should not affect any other aspect of the test, considering nothing really was changed except for cylinder deactivation modes regarding the engine change.

 

Of course, another change is 10 speed vs 8 speed. I'm not sure how that would affect gas mileage, but if the AFM model had to downshift out of 8th to cruise (I didn't see any mention of that for the flat grade testing, which is where the engine uses V4 mode, and the largest mpg difference was observed). I can't imagine having additional gears between the 8th double OD and OD could hurt gas mileage, either.

 

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[the wanderer]

Well, one difference might be the tuning/software. I had one of my cars tuned by a pro back when I thought it was cool, and they can definitely change the tune for different octanes. Exact same hardware, different software, different results running the various octanes. So no guarantees that the older engine would behave the same as the newer one.

[chinookmtp]

Had my 2019 AT4 with 6.2 since Sep 2019. Major reason for 6.2 was it was the only way to get 10 speed tranny on 2019 models. I had the 8 speed in my 2015 6.2 SLT..the tranny was crap, one of the many reasons I no heartburn with trading it.

I have just over 10k miles combination rural/city/highway. Getting average of 18-19 mpg. Get a little better with highway trips..20-22 mpg. 24.5 is best mpg I have gotten, but it doesn't take many hills to pull that average down.

[Grumpy Bear]

On 5/20/2020 at 10:51 AM, Ferrari Eater said:

Which engine is better? I assume the 6.2 has more power and the 5.3 has better mpg, but how much of a difference is it?

Define what BETTER means to you and you will have your answer. 

[CamaroVetteGuy]

The 6.2 is a beast of a engine. No argument. If money and availability were not a factor I might have one. That being said I find the 5.3 to be a great engine. I don’t do much towing so the power is more than adequate for my needs. It just depends on what you want or plan to use the truck for.

[AsapAT4]

What’s real world gas mileage difference between the 5.3 and 6.2?

I’m heavily interested in an AT4 don’t mind the cost of premium as that’s what my bmw takes now. But wondering about gas mileage differences...

[Mikedfw]

What’s real world gas mileage difference between the 5.3 and 6.2?

I’m heavily interested in an AT4 don’t mind the cost of premium as that’s what my bmw takes now. But wondering about gas mileage differences...

I average 18-18.5 on my 6.2 denali, the at4 gets about 1 mpg less. My driving is mixed with probably 60% highway. I do have a heavyish foot.

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[TXGREEK]

I’ve had both the 5.3 and 6.2, the 6.2 gives better mpg’s and overall better driving experience. The 6.2 runs much better on premium fuel and a whole lot more smiles per miles and you cannot deny that the 6.2 is much better at towing.


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[Supercup]

4 hours ago, AsapAT4 said:

What’s real world gas mileage difference between the 5.3 and 6.2?

I’m heavily interested in an AT4 don’t mind the cost of premium as that’s what my bmw takes now. But wondering about gas mileage differences...

I have 2019 AT4 - I get 13-15 around town and 15-18 on the road - I have 2" level kit up front - cost me about 1 mpg - still have stock 275/65/18 Duratraks -   I have never had a tank where I exceeded 18 mpg, but have had 50 mile stretchs of up to 21 mpg.  I have 6,500 miles on my truck and have averaged 14.3 mpg since day 1.  That is 2 mpg better than my 2014 Raptor got, similar driving cycle.  I don't drive for mileage, but if I did I think I could add a couple mpg to my stats.   

[TXGREEK]

Forgot to mention, I’ve got a lifted truck, 33” KO2’s and a 6.2, I get consistent 19-20mpg @70mph highway speeds and 12-14 city.

My last 2014 5.3 gave 15-17 mpg highway and 3-4mpg towing a 7k# trailer.

The 6.2 is a much better fit motor for those that want the max out of their trucks.


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