6.7 Cummins Fuel Economy After a Delete: What We Won't Tell You

You came here for a number. We are not going to give you one, and that is the honest answer rather than a dodge.

Fuel burn on a diesel moves with load, gearing, tire size, weather and your right foot. Change one part and you have moved a single variable inside a dozen. Anybody handing you a clean figure has quietly ignored the other eleven.

What we can be exact about is the hardware. Which pipe fits your year, what arrives in the box, what it costs, and what the job takes on the floor. Let's break it down.

Why Does a 6.7L Cummins Burn Fuel Cleaning Its Own Filter?

The stock exhaust routes through a DPF that traps soot, then burns it off in regen cycles that waste fuel and heat your engine. Every regen burns extra fuel at high EGTs, and the filter eventually clogs anyway. Once the filter clogs, regens run longer and EGTs climb.

What a regen cycle actually does

An engine has a short list of jobs it cannot skip. To operate effectively and safely, the engine must continuously deliver air, fuel and lubrication to the cylinders.^[1] Cleaning a filter is not on that list.

Soot builds until the truck decides to do something about it. Then it injects extra fuel, drives exhaust temperature up, and holds it there until the soot turns to ash. In diesel engines, internal combustion results in expansion of high-temperature, high-pressure gases, which in turn move pistons, transforming chemical energy into mechanical energy.^[1] Fuel spent on a regen never gets that far.

It goes out the pipe as heat. That is the part nobody puts on a spec sheet.

Why a loaded filter costs more than a clean one

Here's the thing — a regen is not one fixed cost. It grows.

A fresh filter lights off, burns clean and gets out of the way. An older one takes longer to come up to temperature and longer to clear, so the truck spends more of its life mid-cycle. Mid-cycle is the expensive part.

Same truck, same route, more fuel. And no warning light tells you it is happening.

The symptoms an owner notices first

You feel it before you ever measure it. Heat comes first — the gauge sits higher than it used to and takes longer to settle. Then the idle that will not come down, because the truck is trying to finish something.

Then the fuel gauge. Not a cliff, a drift. Most guys notice the drift months after it started, which is exactly why the internet is full of confident numbers that do not agree with each other.

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What Changes in the Exhaust When the Filter Comes Out?

A 4" delete exhaust removes the restriction entirely. This is a downpipe-back system in high-quality aluminized steel that replaces the factory DPF and CAT with a straight, free-flowing pipe. Without that backpressure your Cummins breathes freely, EGTs drop under heavy loads, and fuel economy improves noticeably. In Fixed Geometry Turbochargers, exhaust gas flows through the volute in the turbine housing, directing 100% of it to the turbine wheel.^[2]

What backpressure costs you under load

Backpressure is the tax the exhaust charges on every single stroke. Push against a restriction and the engine spends effort breathing out instead of spending it moving the truck.

Take the restriction away and the turbine has an easier job. Spool arrives sooner. Heat leaves faster. The good news? None of that depends on a single number anybody has to promise you.

Where the exhaust gas actually goes

The turbine end is where a pipe earns its keep. The turbine wheel's design and the volute shape are crucial for optimizing turbocharger and engine performance across various speeds and loads.^[2]

Which means the shape of what sits behind that wheel matters as much as the diameter of it. A pipe that opens up at the turbo and then chokes down again further back is a leaky roof with one new side.

Why a bigger pipe is not just noise

A lot of guys assume diameter is about sound. Sound is a side effect.

Volume is the point. A larger cross-section moves the same mass of gas at lower velocity and lower pressure, and lower pressure at the turbine is the thing your engine actually feels. The note changes too, and anyone standing behind the truck will tell you so.

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Will a DPF Delete Give You a Number for MPG?

Nobody can hand a 6.7L Cummins owner one honest miles-per-gallon figure for a DPF delete. Most owners notice real fuel economy gains once the regens are gone. Regen cycles waste fuel and stress the engine, and a failed DPF gets expensive. In a common rail setup, diesel fuel is stored in a high-pressure rail that supplies fuel to each injector independently.^[3]

Why one owner's number is not your number

Two trucks, same year, same pipe, two different answers. One runs empty on flat ground and the other drags weight all day. One sits on stock rubber and stock gearing, and the other does not.

Age is the other half of it. The first-generation 6.7 Cummins is a workhorse, but the DPF system was still new and failure-prone on these years. A truck that has been fighting its filter for years has a different starting point than a fresh one, so it has a different ending point too.

What the regen cycle was costing before

Here is the honest way to say it. You are not gaining fuel. You are stopping a leak.

If the truck was regenerating constantly, that fuel stops. If it was barely regenerating at all, less stops. Same part, two outcomes, and the difference was already sitting in your truck long before the box showed up.

We get it — that is a far less satisfying answer than a number. It is also the one that survives contact with your own fuel log.

The variables that move fuel burn either way

The other half of the fuel question lives on the injection side, not the exhaust side. That rail is the whole reason a modern diesel can meter fuel the way it does. This approach ensures a constant and consistent high pressure, allowing for precise control over fuel injection timing and quantity.^[3]

So the exhaust is one input among several. Want to know what your truck actually does? Log a full tank the same way, twice, before and after, and stop reading forums.

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Which Exhaust Fits Your Model Year?

The 5" Exhaust DPF Delete fits the 2008 through 2012 Dodge Ram with the Cummins 6.7L. The 4" Full Exhaust System covers 2013 through 2018 in aluminized steel. The 5" Full Exhaust System covers the same years in T-409 stainless. The 4" Full Exhaust System for the newer chassis covers 2019 through 2024. Pricing starts at $699.00.

Reading your model year before you order

Read the year off the door jamb, not off memory. A bracket boundary is not a suggestion, and the year on that sticker decides the pipe before anything else does.

Not sure which bracket your cab and box length land in? Call (888) 830-2588 and we will read it through with you before anything ships.

Where each fitment list stops

Three exclusions matter more than anything else on the older chassis. Does not fit Cab & Chassis, the 5.9L Cummins, or 2019+ trucks.

Read the newer bracket the same way. It fits all cab and box lengths, including HD models, but does not fit Cab & Chassis trucks or 2018-and-earlier 6.7L Cummins engines.

The trucks none of these four cover

Cab and chassis is the one that catches people out. Two trucks can look a lot closer in a photograph than they measure on the frame.

So if your truck came from the factory with a flat deck or a bare frame behind the cab, stop and ask first. That is a short conversation that saves a return.

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How Much Work Is Your 6.7L Cummins Being Asked to Do?

Not every 6.7L Cummins leaves the factory the same. For RAM 2500 and 3500 (equipped with a 68RFE Auto) HP and torque have increased to 370 hp and 850 lb-ft to provide the right power for these models.^[5] HD pickup buyers can get an impressive 1,075 lb-ft of torque.^[5] The 2019 model year introduced HD pickup buyers to 1000 lb-ft of torque for the first time ever.^[4]

Standard output versus high output

Two trucks can wear the same badge and pull very differently. This high-output (HO) rating is offered exclusively in the RAM 3500 equipped with the Aisin transmission option.^[5]

So the badge on the fender is not the whole story. The build sheet is.

What the transmission has to do with the rating

The gearbox sets the ceiling. That is why a transmission shows up in a torque rating at all, and why the rating follows the box rather than the badge on the door.

That matters for exhaust the same way it matters for anything else you bolt on. A truck rated to work harder makes more heat, and more heat is precisely what a restriction traps.

Why cylinder pressure and block material matter here

Underneath the ratings sits the hardware that has to hold all of it together. The latest generation Cummins 6.7L Turbo Diesel is a heavy-duty pickup engine that delivers the power, towing performance, quietness, cold-weather reliability, and serviceability that truck owners depend on every day.^[6]

The block is a big part of that. A Compacted Graphite Iron (CGI) material for the block allows us to increase the cylinder pressure capability while reducing the overall weight by almost 60 lbs.^[7]

Built like tanks, in other words. Which is exactly why it is worth taking the restriction off one rather than trading it in.

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What Comes with the Exhaust You Order?

In the box you get the 4" aluminized steel full exhaust, the OEM-style hangers and clamps, and a step-by-step installation guide. You get the T-409 stainless exhaust, the hangers and clamps, and a step-by-step guide. The 5" system for 2008 through 2012 adds one more choice at checkout. A muffler option is available at checkout if you want to take the edge off the sound.

The hardware that ships with the pipe

Everything that touches the truck arrives in one carton. You get the full exhaust, the hangers and clamps, and a step-by-step installation guide.

The turbo-back layout carries a little more in the box. You get the turbo-back pipe, hangers and clamps, all install hardware, and a step-by-step guide.

That is the whole carton, and it is lighter than you expect.

The one option worth choosing at checkout

Sound is the one thing you pick rather than inherit. A straight pipe is loud in a way that is honest about what it is.

Take the muffler if you spend long days at an event with the truck idling beside you. Skip it if the note is half the reason you are doing this.

Check the carton before the truck goes up

Open the box on the floor, not on your back. Lay the pipe out end to end and count the clamps against the guide before you break a single bolt loose.

Ten minutes on the floor beats an hour under the truck.

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What Should You Expect During Installation?

Nothing here needs cutting to length. OEM-style hangers and clamps lock it in the same way the factory exhaust did, so the fit is clean and rattle-free with no welding. Trucks with airbag suspension will need a routing adjustment. You'll need a compatible delete tune so the ECM stops looking for the DPF.

What to have on the bench before you start

Penetrating oil, and more of it than you think. Factory exhaust bolts have been heat-cycling since the truck was new, and the ones nearest the turbo are usually the worst of the lot.

Jack stands. A long breaker bar. A second pair of hands for the back half. That is most of it, and none of it is exotic.

Downpipe-back, turbo-back, and where the work starts

The two layouts begin the job in different places. This 5" pipe runs straight from the turbocharger outlet, replacing the factory DPF, CAT, and every restrictive mid-pipe section. The 5" diameter flows bigger than a 4" for more volume capacity under load, and the OEM-style hangers and clamps lock it in clean with no welding.

Check which end your system starts at before you crawl under, because that decides which bolts you fight first. The ones up top are the fight, so knowing beats guessing if you are working alone.

The two trucks that need an extra step

Rear suspension is the one thing that changes the routing. The Ram 2500 offers two segment-exclusive rear suspensions: a five-link coil system and an air suspension system.^[9] The Ram 3500 continues to utilize the rear Hotchkiss leaf spring system and offers an exclusive supplemental air suspension system.^[8]

If your truck sits on bags, plan for that adjustment up front. Discovering it at the last hanger, with the pipe already hanging, is how a short job turns into a whole Saturday.

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Which System Should You Buy for Your Truck?

The 5" Exhaust DPF Delete for 2008-2012 runs $849.00 to $1029.00. The 4" Full Exhaust System for 2013-2018 runs $699.00 to $775.00. The 5" Full Exhaust System for 2013-2018 runs $799.00 to $869.00. T-409 stainless stands up to real heat cycles, and OEM-style hangers and clamps bolt to factory mount locations — no welding. The 4" Full Exhaust System for 2019-2024 runs $699.00 to $824.00.

5" Exhaust DPF Delete | Dodge Ram 6.7L Cummins 2007.5-2012

A 2010 Dodge Ram with the Cummins 6.7L takes the 5" Exhaust DPF Delete.

This is the bracket where we would spend the extra money without thinking twice about it. Stainless is worth it on a chassis this age. So is the bigger diameter.

4" Full Exhaust System | Ram 6.7L Cummins 2013-2018

A 2013 Dodge Ram with the Cummins 6.7L takes the 4" Full Exhaust System.

This is the bang for your buck pick in the middle bracket. It is the smallest step up from stock, and it is the same bolt-on afternoon as anything else here. If the truck is a weekend rig rather than a workhorse, stop here.

5" Full Exhaust System | Ram 6.7L Cummins 2013-2018

A 2018 Dodge Ram with the Cummins 6.7L takes the 5" Full Exhaust System.

Same bracket, different truck. If yours works hard and you want the most restriction gone, this is the one to buy. The price step buys diameter and it buys stainless, and on a truck that sees real heat both of those pay you back.

4" Full Exhaust System | Ram 6.7L Cummins 2019-2024

A 2022 Dodge Ram with the Cummins 6.7L takes the 4" Full Exhaust System.

No decision to agonize over on the newer chassis. Free shipping is included, with standard delivery in 8-10 business days and express available at 5-8. Tech support is included and tickets are answered within one business day.

What to have ready before you order

Your model year, your cab and box length, and whether the truck sits on bags. Three answers, and the rest is a short phone call.

You are not in a niche here either. Nearly 70% of all Ram 2500 and 3500 Heavy Duty pickup owners choose the Cummins Turbo Diesel as their powertrain of choice.^[4] Cummins engines have been an option in RAM pickups since 1989.^[10]

That is a long time for one engine to keep earning its place under the hood. It is also why the brackets above are narrow, specific, and worth reading twice before you click.