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Discussion Starter #1
Just bought a l5p sold my lml. Anyway truck gets excellent fuel mileage on hywy but absolutely garbage in town as in 8. I leveled truck on 35’s. I could settle for 11 in town 8 towing but 8 is garbage lol. So is anyone running emissions intact tuning how you liking it pros and cons thank
 

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Just bought a l5p sold my lml. Anyway truck gets excellent fuel mileage on hywy but absolutely garbage in town as in 8. I leveled truck on 35’s. I could settle for 11 in town 8 towing but 8 is garbage lol. So is anyone running emissions intact tuning how you liking it pros and cons thank
tuning would likely make it worse.. tuning increases power.. power needs more fuel .. and a lot of these tunes are fuel heavy...

banks is likely your best bet for an intact way to make more power but it won't fix the fact you are starting off in second gear with 35's..

only way to get back to near stock stop and go MPG is to re gear... and get your RPMs and shift points back to being in the proper power bands..
 

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Discussion Starter #3
I don’t see needing to re gear being stock tires are over 34 inches and stock tire wheel combo weigh 8lbs more then wheels tires now. Also the mileage was this way pre level tire wheels
 

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I don’t see needing to re gear being stock tires are over 34 inches and stock tire wheel combo weigh 8lbs more then wheels tires now. Also the mileage was this way pre level tire wheels
you are likely seeing 8 durning a regen.. I don't see you averaging that unless you have something wrong with your truck of drive like or are a teenager..

however

what I said above stands.. period.. if you keep you emissions in tact
the largest detractor to DPF diesels is regen
regardless of how nice you drive the L5P platform it triggers regen on way more than just soot load.. in fact my truck has NEVER regen'd on soot load.. always on the ~36gal trigger (see my DPF thread)

now.. if you are not new to diesels .. when do the smoke black..
1> under load
2> unburned fuel
3> not enough air
essentially all the above is when the engine is not running optimally

now a simple fact is that most if not all emissions tunes just add fuel (banks adds air too the only kit that attaches to the MAP sensor not just fuel rail) but call banks.. talk to an engineer .. and he will admin you are likely not going to see improved MPG.. why.. increased power.. increased fuel consumption.. period.. and when you hit 36gal of diesel or 800 miles.. even if your are at 2% soot load.. the truck will regen .. period

if you have ever had buddies on non DPF trucks bolt on bigger tires.. they roll coal even if they didnt before
if you have ever added a delete tune you will see black smoke

if you run bigger meat... you will be adding soot load to the DPF and it will regen more often.. period
if you run a tune.. you will regen more often unless the tuner messed with regen then its not an 'in tact' tune

you asked for input.. dont shoot the messenger ..
however prove me wrong .. go out and drop a grand on a plug and play box.. you will be back saying its got worse MPG.. what's wrong....
 

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Discussion Starter #5
No I’m not new to diesel world this is number 6 Duramax however this will be my first go keeping emissions, I’ve talked to Duramax tuner and they say 8 is garbage and I shouldn’t see that on this truck, but I’m looking for someone that has installed there tuning or similar and what they are getting, like I said this mileage was pre tire and wheels and mileage has not changed since doing them. It’s just odd it gets great mileage on highway and garbage in town
 

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And thinking about what you said if tuning won’t get better mileage because more fuel then why does it with delete?
Because you get rid of power robing air choking emissions stuff like egr and dpf

but the single largest increase in MPG on a full delete come from the engine no longer having to do REGEN which is 100% wasted diesel.. that is why when you are driving down the highway doing 70 getting 20mpg on the DIC and all of a sudden it drops to 14.. truck just went into regen dumping raw diesel into the exhaust (ie aint making power) to shoot DPF EGTs to 1000 degrees or more to burn out the soot...
 

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You have other issues. I have a 2020 my SIL has a 2021 and he is still under 2k miles but is happy with his average think it was 15 or so. Here is a screen shot taken a few months ago of mine..

1084451
 

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On open highway 72-75mph I get 20.5 mpg hand calculated. It’s in town it goes to garbage
in the words of cool hand Lukes warden.. 'what we have here is a failure to communicate -- some men just cant be reached'

now I, busadave, stoked, have tried to tell you that 8 ain't normal..(and you are saying it was like this with stock rubber too), I am willing to give the benefit of doubt and say it could still be you are driving like a teenager in town.. but be that as it may... your truck could also be doing way too many regens...

1> you should be doing better.. stock
2> no, a 'tune' aint gonna fix it
3> only ways to get better MPG are to
a> fix you problem...take it to the dealer and tell him/her it aint right... fix it
b> less short trips and 0-60 pulls between lights
c> keeping stock wheel sizes
 

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Is that open road driving though. My work commute is in town
That is everything. Lot of highway most 75 to 85 in West Texas but especially in cold or hot weather at the ranch idling sometimes 5 or 6 hours and slow 4wd as well. I live in DFW ranch is in far SE NM high desert. This truck gets better mileage than any of the others before it most were all oil burners. I have had about 20 new trucks in my life. You do have a problem. All of the miles except the 1st hundred are stock wheels with 35x12.50-20 Ridge Grapplers.
 

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Discussion Starter #16
Well I don’t drive like a teenager so interesting from my experience normally if something is wrong. The fuel mileage tanks across the board right?
 

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Discussion Starter #19
So just to give anyone looking some information around my question since I did buy Duramax tuners emissions intact tuning and have been running it almost a week now. So before tuning truck did well 20.5-21 hywy hand calculated, in town horrible 9.4 was average and towing my 42 toy hauler was around 8 over all I could get 11-12 freeway around 63-64mph. Now tuned my mileage on hywy didn’t change much if at all I’d say just easier to maintain it. But towing I saw increase to 11 overall 13.5 around that 63mph mark. In town I’m seeing 12 unloaded. Hand calculated so far my dic is very close
 

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SO tuning alone got you from 8mpg to 12mpg for in town driving? a 50% gain is huge that is great. And confirmed there was nothing wrong with your truck physically?
 
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