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6.6 Gasser

gearheadesw

By gearheadesw
in 6.6L Gas V8 (L8T)

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SierraHD17 Senior Enthusiast

SierraHD17

Posted
Posted

Tuning an L96 is a proven 40 hp and 40 lb ft bump minimum.  With 3.73s its still not that great to drive because the power doesn't offset the mechanical advantage in something exceptionally heavy and designed to tow heavy.  Yes one of these trucks stock will walk away from an equally stock 6 liter for sure.... hard to say what it does against a mildly modded one like my own... especially with the additional gearing I have at 4.56.. 

 

That said... once parts are more available past this strike BS and whatnot I want that 6.6 in my 2017 with an e92 controller from the 2014 to 2018 half tons running it... full tuning support that way and I could easily do a cam and headers...

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Cowpie Senior Enthusiast

Cowpie

Posted
Posted
20 hours ago, SkidooSteve12 said:

I have checked my MPG at the pump every time. 1st tank was 11.8 mpg and then two tanks were at 12.7 mpg and the last tank was 14.1 mpg. The 14.1 mpg was mainly highway driving at 70 mph. The other tanks were mainly short 10-15 mile drives with a mix of highway and mainly city driving. I have over 1500 miles on it so far and have driven it fairly easy.

 

I will have to find my gas receipts to see what the computer said I was getting for MPG.

So you are saying that the new 6.6L doesn't deliver any better fuel economy than the 6.0L.  My 2015 2500 6.0 has gotten 17-18 mpg on road trips.  Hand calculated was within 1 tenth of DIC every time I checked, so I gave up calculating it.

ShotgunZ71 Senior Enthusiast

ShotgunZ71

Posted
Posted

We took the 5er out on a trip this weekend about 2 hrs from home. Split 50/50 between interstate and rural 2-lane roads. Averaged 7.4mpg for the trip, towing a 42’ 14.5k 5er. Pulled great and had plenty of power when needed.

mookdoc6 Senior Enthusiast

mookdoc6

Posted
Posted
6 hours ago, ShotgunZ71 said:

We took the 5er out on a trip this weekend about 2 hrs from home. Split 50/50 between interstate and rural 2-lane roads. Averaged 7.4mpg for the trip, towing a 42’ 14.5k 5er. Pulled great and had plenty of power when needed.

jeesh...about maxed that puppy out!

ShotgunZ71 Senior Enthusiast

ShotgunZ71

Posted
Posted

Truck is rated for 16600 per the door sticker and my pin weight is under 3000. Don't really need the diesel or dually for what we do. Maybe 8-10 trips a year and most of those are in flatland/coastal regions. The Reese Goose Box was also quite nice, versus having the big, heavy, nasty king pin hitch in the bed of the truck.

 

Later this week, we're going on a 9 hour interstate trip without the camper, so it'll be good to see how the truck performs on a long interstate trip.

SkidooSteve12 Enthusiast

SkidooSteve12

Posted
Posted
On 10/19/2019 at 9:51 AM, Cowpie said:

So you are saying that the new 6.6L doesn't deliver any better fuel economy than the 6.0L.  My 2015 2500 6.0 has gotten 17-18 mpg on road trips.  Hand calculated was within 1 tenth of DIC every time I checked, so I gave up calculating it.

 

Yeah, those are my numbers so far. I was thinking today that my tires were only inflated to 55 psi in the front and 65 psi in the back from the dealer. With the colder temps coming, they are closer to 50/60 for my morning commute. I am going to inflate them to all be at 70 psi. What is everyone else running for psi in their E rated tires?

ShotgunZ71 Senior Enthusiast

ShotgunZ71

Posted
Posted
14 minutes ago, SkidooSteve12 said:

 

Yeah, those are my numbers so far. I was thinking today that my tires were only inflated to 55 psi in the front and 65 psi in the back from the dealer. With the colder temps coming, they are closer to 50/60 for my morning commute. I am going to inflate them to all be at 70 psi. What is everyone else running for psi in their E rated tires?

Mine were at the 60/70 when weather was warmer. Now, like yours were, they are 55/65. I'll add some air before the next trip, also.

Cowpie Senior Enthusiast

Cowpie

Posted
Posted

Wow.  I follow the tire maker load pressure chart and typically inflate 50 PSI all around when empty.  Those inflation pressures on the door pillar assume max GVWR.  

When tires are inflated to higher PSI when empty, a lot more wheel hop occurs and the anti slip has to micro engage to compensate, which leads to less MPG.  I found by running the lower pressures when empty improved handling, braking, and fuel economy.  Ticks off my TPMS and Onstar report, but I didn’t ask for their opinion.

texasnavy05 Enthusiast

texasnavy05

Posted
Posted

I'm clearly doing something wrong if you guys are getting 15-18 mpg.  

 

I've got a single cab 6.0 gasser that gets 10.8-11.1 hand calculated over hundreds of fill ups.  

 

My new 6.6 L gasser (only a single tank of fuel through it) seems to be getting somewhere around 12 mpg.  I'll be able to give some better data after a few more fill-ups.

 

I can get my DIC to read 17-18 when I'm empty on flat ground and cruise set to 70mph, but there's no way I'd ever be able to average that high.

ShotgunZ71 Senior Enthusiast

ShotgunZ71

Posted
Posted

The best I ever saw on a tank on my 6.2 Super Duty was 16.1 on level roads in rural country. On the highway/interstate I've seen 15 for a tank. This 6.6 seems on par with that, but I've got an interstate trip coming up, so I'm interested to see how it does in that situation. Only have 2100 miles so far, but I doubt it will get markedly better. It's about what I was expecting, and I'm happy.

mookdoc6 Senior Enthusiast

mookdoc6

Posted
Posted
8 hours ago, ShotgunZ71 said:

The best I ever saw on a tank on my 6.2 Super Duty was 16.1 on level roads in rural country. On the highway/interstate I've seen 15 for a tank. This 6.6 seems on par with that, but I've got an interstate trip coming up, so I'm interested to see how it does in that situation. Only have 2100 miles so far, but I doubt it will get markedly better. It's about what I was expecting, and I'm happy.

Cool, let us know the MPG's I would think it should get 16-17MPG's interstate?  The truck is markedly bigger than previous model i.e. the front end is like a 4X8 sheet of plywood in size!  I wouldn't even look at FERD 7.3L or old L96 6.0?  This is an almost perfect gasser imo? Being a GDI keep it clean and it will outlast FERD's next 2qty attempts at any HEAVY DUTY Gasser they come up with.   Yeah...the 10speed is coming but for now your stuck with a indestructible powertrain.  Nice Truck! 

SkidooSteve12 Enthusiast

SkidooSteve12

Posted
Posted

I ran empty on the highway with the cruise set at 70 mph for about 60 miles and the "Best MPG for the last 50 miles" screen read 17.2 mpg. That situation is rare for me to run that far empty, usually take my wife's Traverse, but the kids wanted to go for a ride in the new truck. :) And I was really curious what I'd get on a strictly highway run empty.

ShotgunZ71 Senior Enthusiast

ShotgunZ71

Posted
Posted

My "Best Of" so far is 18.7 over 25 miles and 18.0 over 50. The 400 miler is 14.2, but I've not ran it on the highway or without using it as a DD during a 400-mile stretch, so that's a good indication of the mixed mileage.

Sunshine39 Enthusiast

Sunshine39

Posted
Posted

We have had ours a little over 2 1/2 months and mostly short stop and go city driving 1877 mile total and lifetime average 10.9 according to the iPhone GMC app. Does look like it is getting around 12 on a couple of tanks. Did pull our 6600# camper once for about 200 miles and that tank averaged right at 10mpg for the trip.

Like the truck but it is big. Was a challenge parking it in a Drs Parking garage yesterday. Stuck out half a car link next to the small cars in there.

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