Chevy and GMC Duramax Diesel Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
19 Posts
Discussion Starter #1
i am trying to decide what to do with my L5P. I am not happy with certain design features, but overall it is a decent truck to drive. I am deciding whether and how long to keep it.

i am clearly operating this thing in ways that IMO it should have been designed for, but apparently isnt. I am getting 11 mpg not towing, 8 towing. It regens all the time. God knows how many gallons of def fluid i have put in it, i lost track, but it is probably 25 gallons in 12,000 miles.

i could gear it taller, (and buy spare mirrors and harnesses, :)), and keep a bunch of DEF laying around....but I am not sure that would be a good investment.

the question is, i bought this thing thinking it should last 500k miles:

1) would it last that long if driven 'calmly'? and

2) how long will it last driving it hard? Is the wear from a few hundred more rpm and a higher average load going to wear out certain parts very quickly? Or are the parts affected most by the additional load and rpm's largely the bulletproof ones?

for discussion, i presume that the turbo, transmission and torque converter, cylinder walls, maybe rings, would be the things most likely impacted. Are these things that historically break or are they pretty stout? what parts generally fail on older duramaxes?

obviously all the def stuff is garbage, i already know that is coming if i dont find a way around it.

I would think that short block and accessories should be able to handle the extra load and rpm's. i would think the fuel system wouldnt care much.

in the valvetrain world, the rpm's are still really low and they are not load sensitive,

maybe spending more time in boost might be a bit of an issue...

any experience or input would be appreciated.
 

·
Registered
Joined
·
701 Posts
Are you related to a guy named turbo Trenton?


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
34 Posts
I currently have 9K miles on my L5P. I drive 70miles round trip to work, non-highway, with hills through towns. I had set the trip odometer the day I bought it and it's averaging almost 17, including some mild camper towing. Tank to tank I'm seeing better than 18 with regens. I can see as high as 22 in-between regens. They occur about once per tank (that I've noticed).

Camper towing 10K lbs I saw around 12 through the hills of NY and PA. Not flat but no mountains. My DEF usage has been as expected. I refilled it for the first time at just over 6K with it showing 20%. Maybe about 8 gallons thus far.

I don't run the crap out of it but I don't baby it. Either there is an issue or your real hard on it.
 

·
Registered
Joined
·
1,098 Posts
Why are you getting such bad mpg? Heavy foot? Sumpin' don't sound right.

Should be a million mile truck if taken care of. Plenty of them out there towing all day, every day with 1 million +.
 

·
Registered
Joined
·
19 Posts
Discussion Starter #6
yes, i do have a heavy foot by most standards. but even at just 75 on flat highways with an aluminum enclosed trailer totaling less than 9000 pounds, it still only gets around 7.5 towing. I was expecting nearly double that at those speeds with such a light trailer. Certainly 12-13.
 

·
Registered
Joined
·
47 Posts
When towing my trailer I average 14-16 MPG at 70 MPH. Unladen I get 22-25 MPG HWY and 17-18 City. I am at 10K miles, and have not used much DEF.
 

·
Registered
Joined
·
1,880 Posts
1. nobody knows how durable the engine is. If the past is an example, expect hundreds of thousands of miles.
2. Driving a diesel hard is how its meant to be driven, they are meant to work every day. Driving it like a ferrari you cant afford to fix will do more harm than good.
3. Did you expect a new aged 7k pound vehicle to be fuel efficient?

4. while there are many complaints about the driveability of the l5p, you can be pretty certain GM made a robust engine. The change points alone are impressive.

Feel free to trade me straight up for my LMM if you don't want to keep it
 

·
Registered
Joined
·
280 Posts
Change where you get your fuel. It makes a difference as I have found out. If you want mileage then you have to drive like you want mileage no way around that. Start there and if there are no improvements then a visit to the dealer is in order. You are far, far off what we are seeing and what you should be reading about.

I can't imagine why you would tow at 75 MPH but then again I have lived in the crowed Northeast all my life and that just isn't possible. Often the mileage is about the wind load just as much as the trailer weight and at 75 depending on your trailer you have a terrific wind load. I don't care what diesel you own towing at 75 is not going to get you 12-13 MPH!!!!

Gearing it taller is going to increase your RPM's and you fuel consumption. I say this not to piss you off but to help you and that is you don't know what a diesel is and what it is supposed to do. They are designed for low RPM torque and that is where you get maximum efficiency. If you want to run way high in RPM range then get a gas but don't know where you find the torque. Higher RPM's will use up a diesel quicker as they have larger parts which means greater inertia which means they will wear quicker at higher RPM. A formula one car running 14k RPM is a little tiny motor that can spin fast and can do so because it is small and has less inertia.

If you ask me you need to re-think somethings and that doesn't include getting a new truck because you can get any you want and they won't satisfy that your stretching what is possible.
 

·
Registered
Joined
·
22 Posts
I currently have 9K miles on my L5P. I drive 70miles round trip to work, non-highway, with hills through towns. I had set the trip odometer the day I bought it and it's averaging almost 17, including some mild camper towing. Tank to tank I'm seeing better than 18 with regens. I can see as high as 22 in-between regens. They occur about once per tank (that I've noticed).

Camper towing 10K lbs I saw around 12 through the hills of NY and PA. Not flat but no mountains. My DEF usage has been as expected. I refilled it for the first time at just over 6K with it showing 20%. Maybe about 8 gallons thus far.

I don't run the crap out of it but I don't baby it. Either there is an issue or your real hard on it.
i am trying to decide what to do with my L5P. I am not happy with certain design features, but overall it is a decent truck to drive. I am deciding whether and how long to keep it.

i am clearly operating this thing in ways that IMO it should have been designed for, but apparently isnt. I am getting 11 mpg not towing, 8 towing. It regens all the time. God knows how many gallons of def fluid i have put in it, i lost track, but it is probably 25 gallons in 12,000 miles.

i could gear it taller, (and buy spare mirrors and harnesses, :)), and keep a bunch of DEF laying around....but I am not sure that would be a good investment.

the question is, i bought this thing thinking it should last 500k miles:

1) would it last that long if driven 'calmly'? and

2) how long will it last driving it hard? Is the wear from a few hundred more rpm and a higher average load going to wear out certain parts very quickly? Or are the parts affected most by the additional load and rpm's largely the bulletproof ones?

for discussion, i presume that the turbo, transmission and torque converter, cylinder walls, maybe rings, would be the things most likely impacted. Are these things that historically break or are they pretty stout? what parts generally fail on older duramaxes?

obviously all the def stuff is garbage, i already know that is coming if i dont find a way around it.

I would think that short block and accessories should be able to handle the extra load and rpm's. i would think the fuel system wouldnt care much.

in the valvetrain world, the rpm's are still really low and they are not load sensitive,

maybe spending more time in boost might be a bit of an issue...

any experience or input would be appreciated.
This thread is so old, no one's probably following it but with over 2 years and 170k miles on my 2017 Denali dually I can tell you that mine is rock solid. Gets 16-17 empty around town and it's a bad day if I get below double digits towing my 10k fifth wheel. Only bitch I have is having to replace five injectors - 6 and 7 went bad and got smart when 7 went out and replaced the four on that bank. Cross your fingers but NONE of the other L5P gripes I've heard.
 

·
Registered
Joined
·
5,971 Posts
fwiw, some info suggests that the 'injector' issues on L5P's were actually a problem with the electrical connectors.
 
  • Like
Reactions: Noble_dmax

·
Registered
Joined
·
1,206 Posts
@M.A.M. knows all too well about that
 
  • Like
Reactions: M.A.M. and redwngr

·
Premium Member
Joined
·
8,872 Posts
Sure do. No issues with them since, knock on wood


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
229 Posts
In all seriousness, you need a Cummins. The '16 I just sold got 16.3 towing all the time. 22-23 empty. They are WAY better on fuel when towing!
 
1 - 15 of 15 Posts
Top