2020-2026 Duramax L5P Filter Kit Buyer’s Guide (TP1015 / PF26 / A3248C / CF185)

The $12 Filter That Nearly Cost Me a Fuel System

A guy I know bought his 2021 Silverado 2500HD used, right at the 60,000-mile mark where the previous owner had clearly been “good enough” about maintenance. First thing he did was order the cheapest fuel filter he could find on Amazon — a no-name TP1015 for about twelve bucks, because “it’s just a filter, they’re all the same.”

Three thousand miles later the truck started a long crank, then a stumble at idle, then a check engine light. The shop found metal glitter in the fuel filter housing. The Bosch CP4.2 pump — the one that feeds the injectors at over 30,000 PSI through a common rail with no downstream filter — had started shedding its hardened cam followers into the system. The $12 filter saved him twelve dollars. The pump, the injectors, the rail, and the labor to clean it all out ran just north of nine grand.

That’s the thing about the 2020-2026 Duramax that nobody puts on the window sticker: the entire fuel system’s lifespan rests on one cartridge that most people treat as an afterthought. This kit exists because four filters on one truck all go on different schedules, and it’s easy to let the wrong one slide.

The CP4.2 Problem Nobody Talks About

The 2020-2026 L5P carries the Bosch CP4.2 high-pressure pump — the same design that prompted a class-action lawsuit against GM on the earlier 2011-2016 LML trucks. The failure mode is well documented and hasn’t changed: the pump’s internal cam followers rotate in their bores, the hardened surfaces wear through, and metal debris enters the fuel system.

Here’s the part that makes it worse. The CP4.2 feeds the injectors directly through a common rail with no downstream filter. Once debris leaves the pump, it goes straight into the injectors. There is no second chance, no catch screen, no “the filter will get it.” The only barrier between a healthy fuel system and a nine-thousand-dollar failure is the fuel filter sitting upstream of the pump.

That’s why the TP1015 is not “just a filter.” Its whole job is water separation — not just catching dirt, but stripping out the water that would otherwise cavitate and destroy the CP4.2’s internal surfaces. A filter that fits but skips the water-separation layer is a bypass valve with a decorative paper element. It filters nothing that matters.

The 2020-2026 window covers two sub-generations: the 2020-2023 trucks with the original L5P layout, and the 2024-2026 trucks with a revised turbo and intake tract. The four filters — TP1015, PF26, A3248C, CF185 — are unchanged across all seven model years. Same parts, same schedules.

What’s in the Kit — Four Filters, Four Jobs

TP1015 fuel filter (cartridge). The one that matters most. It’s a cartridge-style element that lives in a permanent housing under the truck, on the driver’s side inside the frame rail, just ahead of the fuel tank. You unscrew the cap with a 36mm socket, drop the old element, and drop in the new one with fresh O-rings. Its job is dual: a coalescing layer that makes water droplets merge and fall out, plus the hydrophobic screen that blocks what doesn’t. GM cross-references it as 22937279, 23456595, 23304096, 13539108 — and the aftermarket number that actually matters is the Wix WF10451, because the ACDelco TP1015 and the Wix are made in the same Mann+Hummel factory. Same filter, different box, often $20 apart.

PF26 oil filter (spin-on). The 2020+ L5P uses the PF26, not the older PF2232. Same thread pitch, same rough diameter, but different internals: the bypass valve is calibrated for the L5P’s higher oil pressure, and the anti-drainback valve is a silicone diaphragm instead of nitrile — it seals better cold and doesn’t harden over long synthetic-oil drains. One thing the PF26 does not have going for it is size. Among the big three diesel trucks, the Duramax oil filter is the smallest — on a 10-quart sump. Less media surface area means less margin. You don’t cheap out on a filter this compact.

A3248C air filter. The 2020+ trucks got an updated airbox, which is why the 2017-2019 filter doesn’t fit. This is the element that feeds the turbo, and on an L5P that runs a variable-geometry turbo pulling serious air under load, a restrictive or leaking filter chokes power and lets unmetered dust into the compressor wheel. It’s also the cheapest insurance in the box.

CF185 cabin air filter. The one everyone forgets until the A/C smells like a barn. This is an electrostatic element that grabs diesel soot, pollen, and road dust without choking airflow through the HVAC. It’s a 12,000-15,000-mile (or annual) item, and it’s the difference between a cab that smells clean and one that smells like every diesel stop you’ve ever idled at.

What You Actually Pay: The Real Comparison

The 2020-2026 Duramax filter market splits into four camps, and they are not the same product. Prices verified September 2026.

Read it the right way and the value gets simple. Against the GM dealer counter — where the same four filters run $130-160 once you pay the GM logo premium — this kit is roughly 25-35% cheaper and ships as one box instead of four separate trips.

The Amazon bargain route looks cheaper but isn’t the same purchase. The $46.99 and $65.76 three-filter bundles drop the cabin filter entirely — fine, but that’s three-fifths of a service. And the $10-13 no-name TP1015 is the one that started this article: it fits, but cutaway testing shows the critical inner hydrophobic screen is missing entirely, so water passes straight through to the CP4.2. It’s not a cheaper filter. It’s a roulette wheel.

Against ACDelco bought separately on Amazon, the math is honest: you can assemble the same four filters for about the same money — if you’re willing to hunt four different listings from four different sellers and wait for four boxes. This kit’s real pitch is that it’s one box, one order, one part number to remember, and every filter is OEM-spec, not a gamble.

What to Look For When Buying

Fuel filter: Water Separation Is the Whole Point

Oil filter: it’s the smallest one in the class, take it seriously

The PF26 is properly engineered for the L5P’s 10-quart sump and flow rate — but it’s small, and “small” means you don’t have margin for a cheap aftermarket filter with lower media density. Pre-fill it about half to three-quarters full and wipe a little fresh oil on the seal before spinning it on so the engine isn’t starved on first start — then hand-tighten it, not wrench-tight, because the PF26 is one of the most over-tightened filters on the road. The silicone anti-drainback valve is what holds oil in the gallery for the next cold start, and it’s one of the few places where the PF26 is genuinely better than the old PF2232. The drain plug is a 15mm socket (or a T45 Torx on some years) — skip the crescent wrench or channel locks, which will round the bolt head — and torque it to about 18 ft-lb with a fresh gasket, or just snug it firm without over-tightening or you’ll strip the threads. To reset the oil-life monitor after the fill, leave the truck running and use the steering-wheel buttons: press once, scroll to Oil Life, push straight in, then hit the check button to reset it to 100%.

Engine Air Filter: Verify the Airbox Seal

The A3248C lives and dies by its perimeter seal. That seal has to compress airtight against the airbox lid, because any gap is a straight path for unfiltered dust into the turbo. A hard, cracked, or shrunken seal leaks while looking fine. On the L5P, unplug the MAP sensor connector first (pull the red tab, press in, and lift off) before removing the ducting. Unscrew the T20 Torx screws on the airbox cover, insert the A3248C filter ensuring the bottom three tabs and top notch align before pushing it down, and snug the T20 screws back down. Line up the airflow arrow when you drop it in, check inside the intake tube for debris, and reset the Air Filter Life Monitor from the instrument cluster info screen after the swap.

Cabin filter: the one you’ll notice immediately

The CF185 is the only filter in the kit whose effect you can feel — the A/C blows harder and the cab stops smelling like diesel exhaust. If your 2020-2026 truck’s cabin air smells off, or the blower feels weak, the cabin filter has been quietly doing its job past its interval. It’s the cheapest part of the box and the easiest to forget. Swapping it is a five-minute glove-box job: pop the damper rod off the left side, push both sides inward to drop the glove box, then pop the safety clip at the top and slide the filter door off. The CF185 is directional — the airflow arrow points down, toward the blower — so note which way the old one faces before you pull it. Slide the door back until the safety clip locks in, then hang the glove box by inserting its lower holders first and reconnecting the damper rod.

One box vs. four orders

The practical question is whether you want to chase four separate SKUs across Amazon and eBay — a fuel filter here, an oil filter there, an air filter from one seller and a cabin filter from another — or open one box and be done. On a truck you’re keeping past 100,000 miles, the one-box route means you actually do all four on schedule instead of doing two and meaning to get to the rest.

Five Expensive Mistakes

Mistake 1: Buying the $10 fuel filter to “save money”

This is the one that turns a $12 decision into a $9,000 repair. A no-name TP1015 that’s missing the hydrophobic screen is not a filter — it’s a bypass with a paper element. Water goes straight through, cavitates the CP4.2, and the pump sheds metal into a system with no downstream filter to catch it. The fuel filter is the single worst place on this truck to cheap out, and the single cheapest insurance against the most expensive failure.

Mistake 2: Reusing the old O-rings on the fuel filter

The TP1015 cartridge comes with fresh O-rings for a reason. The old ones have been through 60+ PSI of fuel pressure and thousands of thermal cycles — they’ve taken a set and lost their spring. Reuse one and it seals almost well enough, right up until it doesn’t, and you get air in the fuel rail, a long crank, and a stumble that makes you think the pump is dying. The O-rings are pennies. Replace them every time.

Mistake 3: Running the 2017-2019 filter on a 2020+ truck

The 2020+ Silverado and Sierra HD got an updated airbox and filter housing, so the 2017-2019 L5P parts don’t directly cross over — the A3248C is specific to 2020+. Buying the older kit because it’s a few bucks cheaper leaves you with an air filter that doesn’t seal and a fuel filter that doesn’t fit the housing right. Match the part number to the model year, every time.

Mistake 4: Treating the oil filter as an afterthought

On a gas engine, the oil filter is close to an afterthought. On a diesel, it’s the thing catching the soot that would otherwise grind the bearings, the cam, and the turbo’s journal bearings — a turbo that spins past 100,000 RPM on an oil film only microns thick. The PF26 is the smallest oil filter in the class, which means it goes into bypass sooner if you run a cheap low-density filter. Take it seriously.

Mistake 5: Letting the cabin filter ride until the A/C smells

The cabin filter isn’t a performance part, so people let it slide until the cab smells like diesel or the blower bogs down. By then it’s been packed for thousands of miles, and you’ve been breathing whatever it stopped catching. It’s a 12,000-15,000-mile (or annual) item. Change it on schedule, not on smell.

Frequently Asked Questions

What’s actually in this four-filter kit?

The full kit bundles the TP1015 fuel filter, the PF26 oil filter, the A3248C engine air filter, and the CF185 cabin air filter — the four primary filtration points on a 2020-2026 6.6L Duramax. It’s the “do everything in one garage session” bundle, as opposed to the smaller fuel-and-oil or three-filter sets.

Does this kit fit a 2017-2019 Duramax L5P?

No. The 2020+ Silverado and Sierra HD trucks use an updated airbox and filter housing, so the A3248C air filter and the rest of the kit are specific to 2020-2026. The 2017-2019 L5P needs its own filter kit with the older part numbers.

What fuel filter does the 2020-2026 Duramax use?

The TP1015 — a cartridge-style element in a permanent housing, with GM cross-references 22937279, 23456595, 23304096, and 13539108. The Wix equivalent is WF10451, and it’s made in the same Mann+Hummel factory as the ACDelco TP1015.

Why is the fuel filter the most important one in the box?

Because the 2020-2026 L5P runs a Bosch CP4.2 pump that feeds the injectors directly through a common rail with no downstream filter. The fuel filter is the only barrier between a healthy fuel system and metal debris from a failing pump reaching the injectors. Its water-separation layer is what protects the pump from cavitation — and it’s the layer the cheap filters skip.

How often should I change each filter?

The oil filter goes with every oil change (7,500 miles normal, 5,000 severe). The fuel and engine air filters run 15,000-20,000 miles (10,000-15,000 severe). The cabin filter is 12,000-15,000 miles or annually. If your DIC fuel-filter-life monitor hits 0%, change it then regardless of mileage.

Is the PF26 the right oil filter for my 2020+ truck?

Yes. The 2020+ L5P uses the PF26, which replaced the older PF2232 for this generation. It has a bypass valve calibrated for the L5P’s higher oil pressure and a silicone anti-drainback valve. If a listing tries to sell you a PF2232 for a 2020-2026 truck, it’s the wrong filter.

What oil does the L5P take?

GM specifies a 15W-40 diesel oil for the 6.6L Duramax (a 5W-40 full synthetic is fine and preferred in cold climates). Capacity is about 10 quarts with the filter. Stick to a diesel-rated oil with the proper soot-handling additives — this is not a place for bargain gas-engine oil.

Can I just buy the filters separately on Amazon for less?

Sometimes, roughly the same money — but you’re hunting four separate listings from four different sellers and waiting for four boxes, and you’re on your own to make sure each one is the correct part number. This kit’s pitch is one box, one order, and every filter already matched to the truck.

What’s the difference between the ACDelco and the cheap TP1015?

The ACDelco TP1015 and Wix WF10451 are the same filter from the same factory. The cheap no-name TP1015 is not — cutaway testing shows it’s missing the inner hydrophobic screen that does the actual water separation. It fits the housing, but water passes straight through it to the CP4.2.

Why is the Duramax oil filter so small?

The PF26 is smaller than the Powerstroke and Cummins oil filters because the L5P’s 10-quart sump is also smaller. It’s engineered for that oil volume and flow rate, but it means there’s less media surface area — which is exactly why you don’t run a low-density cheap filter on it.

How do I prime the fuel system after replacing the TP1015?

With your foot OFF the brake, press and hold the Start/Stop button for 5–10 seconds to enter Service Mode. You will hear the electric lift pump run to purge air from the housing. Repeat 2–3 times before starting, then let it idle while checking for leaks at the cap and WIF sensor.

Does a new fuel filter make the truck start differently?

A fresh TP1015 with a proper seal and a full prime should fire right up. If you’re still getting a long crank or a stumble after the swap, you likely have air in the line — re-prime it, and check the O-rings and the water-in-fuel sensor seal.

Are these filters good for heavy towing?

Yes — that’s exactly what they’re built for. The fuel filter’s coalescing media handles sustained high fuel flow, the oil filter manages heavy soot load under sustained load, and the air filter feeds the turbo when it’s working hardest. A 2020-2026 Duramax that tows is the truck that benefits most from doing all four on schedule.

Get All Four Filters, in One Box

If your 2020-2026 Duramax has been running on a mix of “whatever was on sale” filters, or you’ve been meaning to get to the cabin filter for three oil changes, this kit closes the gap. One order puts the TP1015 fuel filter, PF26 oil filter, A3248C air filter, and CF185 cabin filter in a single box — matched to the truck, OEM-spec, and ready for one afternoon in the garage.

Get the 2020-2026 Duramax 4-Filter Maintenance Kit

Want to confirm fitment against what other owners are running? A few threads worth reading:

• 2017-2026 6.6L Duramax Fuel Filter — Replaces TP1015
• 2020-2026 6.6L Duramax Oil Filter — Replaces PF26
• 2020-2025 6.6L Duramax Air Filter — Replaces A3248C
• 2020-2026 Silverado Sierra Cabin Air Filter — Replaces CF185

Legal Disclaimer

This guide is for general informational purposes only and is not a substitute for your vehicle’s factory service manual or the advice of a qualified diesel technician. Always verify the correct part numbers for your specific model year, VIN, and configuration before purchasing or installing filters. Installation of any aftermarket or replacement part is performed at your own risk; the author and retailer assume no liability for damage, injury, or loss arising from the use of this information or the products referenced. Filter change intervals are manufacturer recommendations and should be adjusted for your driving conditions, towing load, and fuel quality.