6.6 Gas MPG

kenny_r · December 4, 2019

If they're able to add 1mpg to this truck with such noticeable size, power and capability increases they've done a phenomenal job in my book. The stats on the new 2500 make my 2016 look like a toy.

Too bad it’s just a much larger truck in general....kind of a turn off for me as it won’t fit in my garage. Pretty crazy though with how capable that lil small block is.

Cowpie · December 4, 2019

The primary reason I have used E85 almost exclusively for the last 3 years in mine is, even with the lower mpg, it is still a lower cost per mile than regular.

In the last couple of months, the price spread between fuels is not as good, so I am now using E30. I get almost as good of mpg as with E10, yet the cost is lower. So I am still coming out at a lower cost per mile than E10 and certainly E0 regular. And E30 still has a 93 octane rating so I get the benefits of that. Runs great on it.

2020-2500 · December 4, 2019

I got 19.0 mpg over 178.4 miles recently - though this is probably not repeatable. I was driving on flat land, avg around 55mph and don't see that happening very reliably.

I'm getting between 8.5 and 9.0 mpg when towing a 8500lb travel trailer.

Cowpie · December 5, 2019

14 hours ago, 2020-2500 said:

I got 19.0 mpg over 178.4 miles recently - though this is probably not repeatable. I was driving on flat land, avg around 55mph and don't see that happening very reliably.

I'm getting between 8.5 and 9.0 mpg when towing a 8500lb travel trailer.

Does anyone realize how lame getting that kind of mpg is? Today, my 70' long, 13.6' tall, 32,000 lb semi truck hauling 26,000 lb of cargo in a 53' trailer got about 8.7 mpg for the day. And that motor now has 1,046,619 miles on it. A pickup, even a gasser, yanking around 8500 lb of trailer should beat that by quite a margin. GM is really not getting things right.

kenny_r · December 5, 2019

A new diesel pickup isnt gettin much better mpgs with the same weight. Maybe 11-12

ShotgunZ71 · December 5, 2019

23 hours ago, 2020-2500 said:

I got 19.0 mpg over 178.4 miles recently - though this is probably not repeatable. I was driving on flat land, avg around 55mph and don't see that happening very reliably.

I'm getting between 8.5 and 9.0 mpg when towing a 8500lb travel trailer.

That's pretty good. Mine averaged about 8.5 with my 9500lb TT and now 7.5 with my 5th wheel.

ShotgunZ71 · December 5, 2019

8 hours ago, kenny_r said:

A new diesel pickup isnt gettin much better mpgs with the same weight. Maybe 11-12

Exactly, there best mpg improvement over gasser is on the highway, unloaded. In town, stop and go, the gasser is as good or better than the diesel. I've seen overall about 2 mpg difference overall between my Duramax and both the Ford 6.2 I had and the new 6.6 gas engine.

Donstar · December 5, 2019

10 hours ago, Cowpie said:

Does anyone realize how lame getting that kind of mpg is? Today, my 70' long, 13.6' tall, 32,000 lb semi truck hauling 26,000 lb of cargo in a 53' trailer got about 8.7 mpg for the day. And that motor now has 1,046,619 miles on it. A pickup, even a gasser, yanking around 8500 lb of trailer should beat that by quite a margin. GM is really not getting things right.

Great point. I am sure that GM could introduce a truck with an engine and gearing that would achieve superior gas mileage but it wouldn't sell. Consumers want their trucks to be able to pass a line of traffic going up a steep hill in high gear! I think it would be a blast to have a proportionately geared and powered pickup! However, like your semi, it would require skill and patience to drive.

CRApex · December 5, 2019

2 hours ago, ShotgunZ71 said:

Exactly, there best mpg improvement over gasser is on the highway, unloaded. In town, stop and go, the gasser is as good or better than the diesel. I've seen overall about 2 mpg difference overall between my Duramax and both the Ford 6.2 I had and the new 6.6 gas engine.

I have a 2020 Gas and a 2020 Diesel. The diesel does much better MPG in my experience so far. Towing and empty. Maybe that will change by a wider gap or tighten up a bit once they are both fully broken in..we'll see.

CRApex · December 5, 2019

19 hours ago, Cowpie said:

Does anyone realize how lame getting that kind of mpg is? Today, my 70' long, 13.6' tall, 32,000 lb semi truck hauling 26,000 lb of cargo in a 53' trailer got about 8.7 mpg for the day. And that motor now has 1,046,619 miles on it. A pickup, even a gasser, yanking around 8500 lb of trailer should beat that by quite a margin. GM is really not getting things right.

Really not an apples to apples comparison. If all GM was trying to do is get good mileage while towing, I'm sure they could do better. But the fact is there are sources like TFL truck and others that drag race them loaded and unloaded and like it or not how they perform in these tests help sell them. And I'm willing to bet most people will give up some MPG to have them perform well in all scenarios. So given the size of these trucks and the wide range of how they are used and what most buyers demand, I wouldn't flat out say GM is not getting things right.

Edited December 5, 2019 by CRApex

kenny_r · December 5, 2019

The one thing they got right though is putting the large fuel tanks on the 6.0 HD’s because I’d hate to fill up every 80 miles [emoji23]

IdoMRI · December 5, 2019

5 minutes ago, kenny_r said:

The one thing they got right though is putting the large fuel tanks on the 6.0 HD’s because I’d hate to fill up every 80 miles

LOL very true, when I had my gasser HD I hated not having a larger tank especially when towing.

ShotgunZ71 · December 5, 2019

1 hour ago, CRApex said:

I have a 2020 Gas and a 2020 Diesel. The diesel does much better MPG in my experience so far. Towing and empty. Maybe that will change by a wider gap or tighten up a bit once they are both fully broken in..we'll see.

My overall average mileage includes highway, rural, town, DD, and towing. The diesel was 2 mpg better overall over 24,000+ miles. On the highway and rural driving it would be 4-5 mpg better than the gas, but in town and stop and go, the gasser was better by 0.5 normally and when towing the TT the diesel was 2-2.5 better. On an all-interstate trip, the diesel was better by roughly 3 mpg. The new 10-speed will make some difference, but I'm not sure if it will be appreciably better compared to the previous Allison 6-speed. The final drive dropping from 3.73 to 3.42 will also make a difference.

Edited December 5, 2019 by ShotgunZ71

Pastusak.t · December 6, 2019

On 12/4/2019 at 9:39 PM, Cowpie said:

Does anyone realize how lame getting that kind of mpg is? Today, my 70' long, 13.6' tall, 32,000 lb semi truck hauling 26,000 lb of cargo in a 53' trailer got about 8.7 mpg for the day. And that motor now has 1,046,619 miles on it. A pickup, even a gasser, yanking around 8500 lb of trailer should beat that by quite a margin. GM is really not getting things right.

I really can’t believe these comments. If a manufacturer had the ability to make a truck that would blow away the competition in mpg do you really think they would just say, “naw, I don’t want to give the people what they want.” No. I’m not saying a better fuel economy isn’t possible but there has got to be a limiting factor. Its either too expensive and people wouldn’t buy it. Or not been proven to be reliable and they would have too much in warranty repairs. The epa and governmental agencies are breathing down all auto manufacturers necks to improve mpg and to say that they can make it better and just refuse to do it is ridiculous.

Cowpie · December 6, 2019

2 hours ago, Pastusak.t said:

I really can’t believe these comments. If a manufacturer had the ability to make a truck that would blow away the competition in mpg do you really think they would just say, “naw, I don’t want to give the people what they want.” No. I’m not saying a better fuel economy isn’t possible but there has got to be a limiting factor. Its either too expensive and people wouldn’t buy it. Or not been proven to be reliable and they would have too much in warranty repairs. The epa and governmental agencies are breathing down all auto manufacturers necks to improve mpg and to say that they can make it better and just refuse to do it is ridiculous.

The average mpg of commercial semi trucks has almost doubled in the last 20 years. Doing the same work on the same terrain in the same weather. And the average HP and Torque of engines has gone up as well. Meanwhile, the average trailer length has gone from 48' to 53'. Even with all the diesel emissions stuff that got piled on just like the pickups got. And there was no government CAFE stuff forcing OEM's to improve mpg of semi trucks over that period. The heavy truck OEM's did it to gain market share. They did it to improve customer cost benefit ratios. They put their R&D people to work.

The OEM pickup manufacturers cannot make the same claim to have doubled average mpg in the last 20 years of pickups within any class. A little bit of an uptick, but certainly not doubled. And it wouldn't have improved much at all if the pickup OEM's had not had the government breathing down their throat about fuel economy. My '98 2500 454 averaged 12-13 mpg for all miles . My 2015 2500 6.0 only gets about 1-2 mpg average better fuel economy than that for all miles. And the new 6.6 gasser numbers have not added much to that. If the pickup OEM's had accomplished the same thing as heavy commercial trucks, the average MPG for all miles of a modern 2500 gasser would be at least 20 mpg. That average including highway, city, hauling, everything. Diesels in pickups would be averaging in the high 20's mpg for all miles as well, not just highway mpg.

The average price of a new pickup has virtually doubled in the last 20 years though. Even while the average price of a new heavy commercial truck has only gone up 50% in comparison. So the pickup OEM's have exceeded the cost growth compared to heavy commercial trucks.

Edited December 6, 2019 by Cowpie