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All,

With the new EPA crackdown on diesel tuning I am coming to terms with running all emissions equipment intact on my work/family truck. Currently I drive a 2016 6.7 cummins, but with all the weight it lost, my desire for a new and flashy truck, and the current lack of "tuning" options....I am at an fork in the proverbial road. I drive a lot more than I tow for work, since its a personal vehicle....the depreciation of a gasser has put me in diesels for a number of years, over a course of 4 months I have put 20k on this truck (far from the highest, but way ahead of low use) and will stick with the diesel truck world. Weekly trips around the state range from 200 miles, to 1200 miles and idle times vary (at one point my last truck didn't turn off for 13 hours). Couple that will frequent drives to TN and GA to visit family, I can really rack up miles.

I have always liked the way the GMs looked, and the new 2020 (as well as the 2019) just seems to be right up my ally....but it leads to a huge question, how is everyone fairing with the emissions? Everyone on the inter webs spits out hatred for the emissions, how the trucks will be (or are) unreliable, and that losing some weight is the only real option....BUT, accepting that the EPA has cracked down on the sales and distribution, in all honesty, I don't feel like messing with emissions bypassing.

Is everyone happy with the L5P? How are the regens? Anyone up to or over 100k that can chime in on the longevity of the emissions system? By design, will proper maintenance (or in this case driving) lead to a long happy emissions life?

I don't worry so much about the power-train lasting, but emissions longevity really give me pause prior to dumping the 64k on the 2019 (old style) Denali my wife and I just drove (or the 72k for the 2020 AT4).

Gonna continue to read as I wait for responses, thanks for all the intel anyone can provide, its a big decision, and first hand knowledge is appreciated.

VR

Corbin
 

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** I'm going to follow this thread. **

I have been reading and researching diesels for a few years now...coming from a 2004 2500HD 8.1/496/Allison gas.

Really wanted to get LML Duramax, but the high price of used and the CP4 pump issue cause me to hesitate. I fully planned to delete the emissions and drive it in to the ground. If it weren't for the CP4 issue, I would probably be in an LML right now.

Knew that the 2019's would be dropping in price with the 2020's coming out. Glad I waited...

Used 2500HD Crew Cabs in LTZ trim were in the $54-59k range. Throw in extra $$$ for delete and CP3 conversion...nope that just wasn't going to fit in the budget.

Last week I pulled the trigger on a 2019 LTZ that had almost all the options on my wish-list.

Incentives and discounts knocked 20% off MSRP...it was $66k and some change, got down to $52,572...but not low enough. Talked to dealer in to throwing in tonneau cover, bed mat, mud flapps, floor liners, under seat storage, window tint. I'm happy.

Other truck I was looking at was a 2016 LTZ with 27k miles...they wanted $51,950...no brainer to get the new 2019!

I never really looked at 2020 HD's, as they are longer and will not really fit in my garage. And I am not a fan of new tech...would rather wait and see how the new 10 speed does behind the 2020 Duramax.

Interested to see what others are seeing from their L5P's...
 

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Welcome to the site first off!!! I think as in my case the 19 truck has most of the emission bugs worked out, (Knock on wood) I'm at 33,XXX miles on my truck in 13 months, and I've not had any issues with the emissions at all. At the same millage on my 2011 (first year) I had been to the shop 4 or 5 times and had replaced the DEF tank twice, once by GM the other was my fault.
I drive 10 miles each way to work, the first 7 to 8 is open road at 60 Mph, the last 3 to 4 is stop and go small town with 8 stop lights to deal with, if this is all the driving I do this truck will regen at about 300-350 miles it will do something that my 2011 would not do and that is regen at low speeds 30 mph in stop and go traffic. In my thoughts if you want a diesel the L5P is the only one to have!! On the highway empty at 75-80 Mph I can go 808 miles before it does a regen, that 808 number has been the max milage the truck has ever gone and it has done it muiltupe times.
 

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..... We got a 2019 Dually Denali 3500 with 11.7K miles since End of April, usually 1400# over GVWR with our TC loaded.... Rides great loaded and absolutely NO ISSUES so far..... But I drive slow & easy with no pedal to the metal... Mostly highway and back country roads in the Western states.... In case you are unaware it’s an Isuzu design motor....2nd one for me....
 

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Having owned my LB7 since new, I'm not super knowledgeable about emissions gear but I have also been looking to upgrade to a new truck... so I have been reading and asking questions for almost 4 years now. From what I can tell, the emissions systems on the L5P are pretty trouble-free. Been watching and reading everything I could since before they were into'd in '17 and I can tell you that the horror stories with emissions just have not been there with the L5P like previous models.

I've pretty much decided that I will buy a '21 or '22 and am pretty satisfied that the L5P is solid. The new 10 speed has yet to prove itself but it's getting VERY high marks right now and even though Allison isn't building it, they did put their name on it so that gives me some confidence there.
 

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What makes me apprehensive is the out of warranty issues. Emission systems taking a crap is EXPENSIVE. I'm honestly not worried about them failing in warranty.

I tend to keep my vehicles until they are pretty much run to death. I don't know if that will be possible with new diesels since deleting them is becoming not an option.
 

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21k on my L5P zero issues. I worry most about egr carbon buildup but can’t find any info anywhere on it. Maybe that’s a good sign.

It does have a built in oil separator maybe that helps with the buildup.

I regen at least once a tank I think and it’s mostly cruising highway country roads and commuting long distances to work 500 miles one way each week. Should be easy life for it I hope and hope it lasts.


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The GDI, AFM, DFM gasoline engines have their own set of expensive issues. I'm not sure we can dodge the long reach of the EPA.
Agreed. I looked long and hard at transitioning to a 1/2 ton Silverado. Four things worried me:

1. AFM/DFM: Maybe I read too much on the inter-webs, but the cylinder deactivation scares the crap out of me.
2. 8 speed transmission: Known issues with this GM transmission. And the majority of 1500 Silverado's I was looking at came with the 8 speed. Nope.
3. Auto start / stop: I know it saves fuel, but I just cannot stand when vehicle shuts off at stop light. Yes, you can deactivate the system...
4. Going from 3/4 ton to 1/2 ton: I actually prefer the ride of the 2500HD's vs. the 1500's. I had two 1500's back in the day ('99 and '01), and they were great trucks. The HD was just so much better. And when it comes to capability of my truck, I'd rather have it and not need it, vs. need it and not have it.
 

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Same situation as DaubsNU1
I am a Chevy guy this is truck number 9 over the years
1970 was first used in highschool
Had a 1982 6.2 diesel 250,000 miles before I sold it
Needed a 2500 to pull a 5th wheel
Got a deal on the 2019 LTZ Z71 loaded
Only 5000 miles on it // love it so far...
 

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Had a '17 6.2 8spd max tow, loved that truck except for the trans shudder. (I cured it with a different trans fluid)
Next was an '18 Denali L5P, no issues. Highway it would go 700+ miles before regen, around town it could be as short as 100mi to regen or up to 250mi.
Now in a 2020 AT4 L5P, first regen was mostly around town driving it went 700mi. Leaving today for a 1300mi trip towing our 5th wheel, I'm really looking forward to towing with the 10spd.
 

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What makes me apprehensive is the out of warranty issues. Emission systems taking a crap is EXPENSIVE. I'm honestly not worried about them failing in warranty.
The GDI, AFM, DFM gasoline engines have their own set of expensive issues. I'm not sure we can dodge the long reach of the EPA.
Yeah I know. I'm still thinking long and hard before I buy anything.

Maybe Ford was right by going with an old school large displacement, 2 valve, pushrod v8 gas engine.

Yeah I know it can't tow as much, that was partly sarcasm
 

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I worry most about egr carbon buildup but can’t find any info anywhere on it. Maybe that’s a good sign.
Look at the last few pages of Matt's info dump thread. He posted some shots of his EGR buildup at 250,000+ miles. Looked scary, but I don't think he posted anything negative about drivability because of it. I have not read every post in that very long thread.

https://www.duramaxforum.com/forum/10944554-post1.html

I'm only coming up on 20K on my '19 with no issues whatsoever. While nothing mechanical or electrical is bulletproof, the L5P systems seem to not have many problems. (Don't know what it is with the '20 DEF level issue. It's a fluid level sending unit. How hard could that be? Use the same one you've been putting in fuel tanks for the last 50 years.)
 

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Wow, thanks all for the replies. Im trying to absorb as much information about the L5P as its one heck of an expenditure! Heck, if my wife had her way, the AT4 we drove would be parked next to her JLU in the driveway.

800 miles on the interstate before a regen sounds very promising as most of my miles are interstate for work. To be honest, the only miles I put on that aren't interstate are occasional around town trips and drives to the local VA medical center (Dorn right here in Columbia). But even Dorn is an 11 mile I77 drive at 70mph.
 

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I do mostly highway and just a little in town and it still seems to do it once a tank or more. I don’t precisely track it and it’s seamless. Just notice mpg dropping like rock for 15 mins.

I need to read that link yea it’s long. If you only have to clean the carbon once (in its 500k or so Highway life) then that’s not too bad. I dunno how you would clean from valve area.


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I do mostly highway and just a little in town and it still seems to do it once a tank or more. I don’t precisely track it and it’s seamless. Just notice mpg dropping like rock for 15 mins.

I need to read that link yea it’s long. If you only have to clean the carbon once (in its 500k or so Highway life) then that’s not too bad. I dunno how you would clean from valve area.


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Well the drop in mileage something I was expecting based on how the emissions work, glad to hear it isn't crazy long (some ford people told me they were seeing times as high as 30 minutes).

EGR cleaning shouldn't be too bad if its accessible like the 6.7 powerstroke I had (prior to this cummins)..though you are correct, from the valve side would be difficult without pulling off major components.
 

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..... In case you are unaware it’s an Isuzu design motor.
Actually, it was designed as a joint venture between GM and Isuzu. After the first couple of years (can't remember the exact number) GM bought out Isuzu's interest in Duramax and has been the sole designer since.

-Mark
 

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I dont own an L5P, however if i had to buy a diesel today that was a current model year and i needed to keep it intact it would be an L5P for the following few reasons.

1: no more CP4
2: new mechanical injectors
3: more power stock than any previous duramax
4: more gears in the transmission
5: most modern, and hopefully, most reliable emissions system to date.



21k on my L5P zero issues. I worry most about egr carbon buildup but can’t find any info anywhere on it. Maybe that’s a good sign.

It does have a built in oil separator maybe that helps with the buildup.

I regen at least once a tank I think and it’s mostly cruising highway country roads and commuting long distances to work 500 miles one way each week. Should be easy life for it I hope and hope it lasts.


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the oil catch is for the PCV system to pull liquid oil out of the crank vapor before routing it back into the intake to be burned. That does not really change the issue with carbon build up in the EGR, since the EGR is recirculating already burned exhaust gas back into the intake. Similar issues, and each one contributes to the overall problem of buildup in the intake, but its not the same issue. You could redirect the PCV to the atmosphere and the EGR would still pump carbon into the intake, there just would be less sticky oil to bind it to the sides of the intake. Same goes for the EGR, remove it and no more soot, but without deleting the PCV you would still get oil in the intake.
 

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Well that’s precisely what I mean. Without oil vapor the carbon buildup would be much less or negligible. If it’s dry carbon it flows through engine harmlessly. Tho some may argue it is harmful but all modern diesels do it.

My hope is the reduction of oil vapor reduces carbon buildup.

An example of bad implementation of all of this is bmw 335D and alh tdis from VW. They both had extreme buildup to point the engine wont run correctly. Especially the bmw. None of them had oil separation.

I’m not sure if some other sorcery like DEF and less EGR action reduces the overall problem.

This all being said the tdis I have cleaned had extreme buildup to point of say 1/2 inch or more all the way around without any noticeable engine degradation. However if that were to break off and go into cylinder trouble will come.


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I have owned numerous makes of diesel trucks over the years. Cummins, Powerstroke, and Duramax. They all have their quirks, as far as emissions system reliability GM has seemingly had a more reliable system from my experience. My previous 2015 and 2019 Duramax trucks you could definitely tell there was a regen going on, higher idle speeds and you could smell it. 2020 I really haven't found any signs other than perhaps decreased mpg and usually it lasts around 15-20 minutes. It may take a few more years, but there will eventually be a complete delete kit for the l5p motors that isn't hard to come by and doesn't require a second mortgage.


So far the 10 speed has been impressive, looking forward to putting it through its paces over the next several years.
 
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