Fuel Mileage L5P

Aaron1085 · April 9, 2018

HOW are you people averaging over 18mpg?! I can’t break 16.5 with 80% city driving. And that’s conservatively driving it.

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Loco-diablo · April 9, 2018

At just 15k on the odometer, my life time mpg is about 18.5 with my 2017 5.3 DC 4x4. That’s about 80% highway 20% city.
I run mid grade 89. I can definitely notice a drop in mpg when my foot gets heavy. The terrain varies greatly in my area also. I expect to to a bit better when the summer grade gas returns.

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FreeAmerican · April 24, 2018

I noticed after one of the ECU upgrades that my lower speed (esp 45mph) shift points changed. Originally I would have to speed up to about 50, let the transmission shift up, let off and drift down to 45.

Now, about 45 or right at it, it up shifts. This helped my around town mpg a lot.

I've noticed the lack of freewheeling too. On my 15 GMC 1500 you could turn it off by holding the tow button for 5 seconds or so. Helped the MPG on the 1500 as well.

I have not found a way to turn it off on my 2500.

powerhaulic · May 8, 2018

10000 miles on my '18 Duramax now, traded the TT for a fifth wheel.

Combined weight truck and trailer 24040lb averaged 11.1 from Fla to NY, fantastic in my book.

No trailer loaded box and tonneau cover did 21.3 on a 1400mi trip running 75mph cruise set.

SilveradoX2 · September 10, 2018

On 11/28/2017 at 7:09 AM, SilveradoX2 said:

Thanks for the info Peterd. I'm thinking of getting a 2018 GMC 2500 HD All Terrain X with the Duramax in Onyx Black.

As to half tons, I can 20 mpg in my 2012 1500 with the 6.2L burning premium with the wife and I plus a hundred plus pounds of luggage & camera equipment on flat ground. Keeping that truck & selling my 2003 2500 HD?.

I know it's early, but... I bought an All Terrain instead of the X for various reasons.

I did a break-in run of 625 miles from Phoenix (1700 ft) to far northeastern AZ (9000 ft). Almost on only one tank. By manual calculation I averaged a little over 18.5 mpg. My 1500 6.2L would have averaged maybe 15 mpg on premium. Since diesel is a whole cheaper in Phoenix than premium, the 2500 is saving me money.

And I'm having fun with the GMC.

Colossus · September 10, 2018

Rule number 1 of owning a diesel- if you get worried over the cost of diesel fuel, don't get a diesel truck. Drive it well and enjoy it, you got a great vehicle.

Edited September 10, 2018 by Colossus

Cowpie · December 25, 2018

On 8/14/2017 at 6:36 PM, Debra in Cali said:

I just returned from a long trip pulling my 5th wheel. I was getting over 12 mpg while towing while on the flat. It was getting around 8-9 going up I-80 to Donner Summit. I have been getting over 22 mpg without towing and around 18 mpg in city driving. This beast has better city mileage than my 2015 1500 got. I am so impressed. I was so expecting that I was going to be pulling around a giant gas hog, just so that we could pull a 5th wheel. I am beyond pleased. And it is not even broke in yet. I can't wait until it is completely broke in to see what kind of mileage it will get.

It is still a pain to park in most small space parking lots, but I am living with it.

It all depends on the fuel cost as to whether the actual cost per mile is there along with the mpg. It is true that the typical diesel will get better mpg in city or highway than most gasser 1/2 tons, but if the cost of fuel is significantly more, it really is just a warm fuzzy and nothing substantive.

For instance, my 2015 6.0 is living on E85 fuel. Sure, really lousy fuel economy of an average 10 mpg for everything. But at $1.10 a gallon for the fuel in my area, that comes out to about 11 cents a mile fuel cost. Diesel in my area is going for $2.76. For the a diesel 2500 to just break even with the cost per mile I get with my 6.0, it would have to average for all miles (highway, city, hauling, etc) a minimum average of 25 mpg. Not going to happen except downhill with a tail wind on the highway.

Just on gas in my area, the cost is $1.90. My 2500 would average about 14 mpg for all miles on regular gas. So that comes out at about 12.7 cents a mile. Again, at $2.76 for diesel, a Dmax 2500 would have to average at least 22 mpg for all miles (again: city, highway, hauling, etc average) just to break even.

So the only real advantage of diesel is pulling power. It certainly is not cost, and in fact, costs more in both original purchase and to operate it. The price for that power. If that power is actually needed, it can be worth it. If not, it is merely a social statement having a diesel, and a high priced one at that. The better mpg feels good, but it is all smoke and mirrors and is actually costing more.

Edited December 25, 2018 by Cowpie
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