Duramax L5P Fuel Mileage

Here you can look at my Fully page, 2018 GMC Denali 3500 srw 4x
L5P fuel logs


Love my L5P, its been flawless!

Comparison is against self. The percent change from solo to towing.

1). Set aside a day. Head out to nearest Interstate fuel stop. Top fuel to first auto shut. Tires at lowest per chart. Nothing in truck. Scale it.

2). 100+ miles outbound and then back to same pump. Top off same way.

3). 100% cruise control at 58/9-mph. (No, not 63 as the aerodynamic wall is dead on 60).

4). Ideal trip is only two accel and two decel events with no lane changes.

This (like getting a TARE weight) is a baseline for all that comes in the future.

Guys getting 17-18/hwy SOLO are cracking me up. I hit 17 Towing my 35’ TT.

Mechanical condition and future diagnosis of problems needs a baseline of numbers.

The PERCENTAGE CHANGE from solo to Towing is predicated on same tow vehicle sans trailer, same roads & speed

OP you’ll find none of the respondents or others you ask will ever have made a comparison worth quoting. Speeds, loads, etc, are ignored. And wrong tire pressures are used. Do your own testing.

The same test as above with the truck loaded for camping (simulate passenger load) AND yet another when hitched (max propane & water ) AT THE SAME SPEED AS ABOVE

Will give you the Scale Info and tire pressure data you NEED to make good decisions. . Changes in mpg are idiot lights. What’s wrong?

The final result is being able to predict vacation fuel costs while towing. At today’s prices I can use Fuel Cost = 17-cpm (cents per mile).

Step One is in finding “best” highway mpg. Solo empty. Solo loaded and then towing.
Use FUELLY or similar to trend.
.

I have a 2018 GMC 3500 DRW Duramax purchased in July 2018. So far I have run about 5,500 miles towing and around 10,000 mile not towing.

Towing avg MPG = 10.7
No Tow avg MPG = 18.8

I just pulled a 40 Aline to the Texas gulf and back computer showed 1 or above the whole trip

I have an 17 3500 dually pulling a 16000 fvr 8.5 in there some where. I just added banks derringer and air filter, also pedal commander. The truck is total different truck now. Now lag when you step on the gas love it.

Mine is a SRW and I pull a 7000lb travel trailer, so not an exact answer to your question, but hopefully it will help.

I've owned my truck for 1 year and it is also my daily driver...it's a 2018 Denali Crew Cab. My computer average MPG for that 1 year is 15.6 for all my driving. Towing seems to be in the 11-12 range, my average weekly tank is around 16.5, and hwy/interstate trips with just the family is 22-23. The DRF cleaning cycle will really knock down your avg mpg for a tank.

chiefneon wrote:

Sheepdog78 wrote:
What’s it getting when not towing?

Howdy!

I don’t know, we tow with it and use the Smart Car we carry in the toy hauler to get around in.

“Happy Trails”
Chiefneon

Good point! I don't really care what kind of mpg it gets.....I just know it gets better than my '06 Cummins got towing a lot let weight.

Sheepdog78 wrote:
What’s it getting when not towing?

Howdy!

I don’t know, we tow with it and use the Smart Car we carry in the toy hauler to get around in.

“Happy Trails”
Chiefneon

laknox wrote:

Sheepdog78 wrote:
Anyone have any real world experience with the fuel economy of the new GM L5P Duramax in a 3500 DRW?

Nope, but I =did= subscribe to one of Gale Banks' videos where they've totally instrumented a new crate L5P engine and are going to keep pushing it until, as Gale said, "the crankshaft's on the floor or the heads are on the ceiling". :B

Lyle

Gale Banks produces some excellent and informative videos. I don't even have a diesel, but I love watching his videos.

Sheepdog78 wrote:
Anyone have any real world experience with the fuel economy of the new GM L5P Duramax in a 3500 DRW?

Nope, but I =did= subscribe to one of Gale Banks' videos where they've totally instrumented a new crate L5P engine and are going to keep pushing it until, as Gale said, "the crankshaft's on the floor or the heads are on the ceiling". :B

Lyle