Diesel Place banner

41 - 60 of 89 Posts

·
Premium Member
Joined
·
125 Posts
2018 GMC 3500HD with 100 miles, mostly short 2-20 miles trips till spring comes.
15 MPG
I am in that same boat...
 

·
Registered
Joined
·
145 Posts
I've gotten as high as 20 or 21 all hwy on fairly flat ground. 19 with mostly hwy but a little stop and go and or slight hills. Now though with winter fuel i'm down to 17-18 in these same conditions. The current tank i'm on currently sits at 15.8 with mostly around town driving and maybe 20% hwy.
 

·
Registered
Joined
·
214 Posts
Hey Kids. Some good numbers here. I recently sold my Ram 5500 and I'm thinking it's time to return to the flock (once I sell my new Tacoma TRD Pro). Time to just have one vehicle for me. Please keep those 3500 dually numbers coming!
 

·
Registered
Joined
·
1 Posts
Got 17.5 mpg on the way home from the dealer but havent hit more then 15 mpg since. About 11.5 after the lift . Wonder if these new tunes will increase mpg enough to justify spending $4500 or are the just for hp/tq gains
 

·
Registered
Joined
·
56 Posts
Roughly 1500mi on truck; cruise control set at 80-85 on long stretches of an 1100mi trip, I saw 15.5-15.7mpg.
 

·
Registered
Joined
·
266 Posts
Agree redwngr, another form of, "you gotta pay if you want to play" :)

With the poor aerodynamic form of big pickups, increased speed kills fuel economy due to air drag so unless you always plan your travels to run with a big tail wind it will cost you. Every time you double your speed on a flat road it takes approximately 8X more horsepower. Normally doubling the rate at which work is done would require only twice the horsepower but because the air resistance follows approximately a square law response you end up with 4 times the air resistance at twice the speed coupled with the need to increase horsepower to do the same work at a faster rate you end up wit the basic 8X equation.

Or put simply, it if takes 10 horsepower to travel 40 MPH your horsepower demand goes up to around 80 horsepower at 80 MPH and you will burn more fuel to generate this power.

So why don't you get 8X the fuel economy at half the speed? The 8X approximation is a pretty close rule of thumb at high speed but at lower speeds you are also overcoming additional drivetrain losses, rolling resistance, any road grade, etc. as you increase speed and the powertrain is designed and geared to produce best efficiency under typical operating conditions. So even at lower speed you aren't going to be challenging a prius in the fuel economy race but at 52-55 MPH you should get in the low 20 MPG range which might be important if you are very low on fuel many miles from the nearest station. On the other hand if you remove the speed governor from the programming and get the truck into the 110 MPH range then you probably will be in the 3-4 MPG range or about what you would get running the truck fully loaded up the Ike with the engine RPM at peak HP.
 

·
Registered
Joined
·
1,257 Posts
So far.........
 

Attachments

·
Registered
Joined
·
214 Posts
3500 SRW. 18.3 on the way home from the dealer.
 

·
Registered
Joined
·
26 Posts
I sure hope my 19 gets better with time. I have 600 miles on it and it doesn't even come close to the 15 I traded in! The 15 would show around 20mpg on cruise at 65mph and the 19 is running around 17mpg on the same road.
 

·
Registered
Joined
·
2,865 Posts
I sure hope my 19 gets better with time. I have 600 miles on it and it doesn't even come close to the 15 I traded in! The 15 would show around 20mpg on cruise at 65mph and the 19 is running around 17mpg on the same road.
Tough to compare a well broken in one against one that is new and running winter fuel.

Mine will runs well over 20 at 65 mph on cruise, flat and no wind.

They do regen more often than LML, but the regen's are shorter.


I'd expect your 65 mph on cruise mpg to improve significantly.
 

·
Registered
Joined
·
26 Posts
I hope you are right. I have had a 06, 11, 13, 15, and now this 19 and I don't seem to remember a big break in period but I could be wrong.

Yea I was surprised when in went into regen at 525 miles the first time and how fast it was done!
 

·
Registered
Joined
·
1,257 Posts
I just got 21.9 mpg (hand calculated) on a trip from North Alabama to the Smokey Mountains. My best, so far.
 

·
Registered
Joined
·
1,257 Posts
About 46k. Mileage improved about 1 - 1.5 mpg after I put the banks Derringer and CAI on it.
 

·
Registered
Joined
·
1,530 Posts
I just got 21.9 mpg (hand calculated) on a trip from North Alabama to the Smokey Mountains. My best, so far.
how fast were you going?
 

·
Registered
Joined
·
1,257 Posts

·
Registered
Joined
·
29 Posts
8.5 hauling a 40' trailer with 2 cars and loads of heavy tools in it. Averaging about 65-70 MPH. Really seemed to suck up the DEF with the big load on it.


Greg
 
41 - 60 of 89 Posts
Top