2020-2025 Duramax L5P Fuel, Oil and Air Filter Buyer’s Guide (TP1015 / PF26 / A3248C)

The $12 Filter That Nearly Cost Me a Fuel System

A buddy of mine bought a 2021 Silverado 2500 HD last spring — 88,000 miles, clean Carfax, no service records. The first thing he did was the “smart” thing: he found a three-filter kit on Amazon for $46.99 and felt like he’d beaten the system. Fuel filter, oil filter, air filter, all in one box for less than half of what the dealer wanted.

Three months later the truck started to stumble on hard pulls. Then it threw a low-fuel-pressure code. Then it died at a stoplight and wouldn’t restart. The diagnosis was a wiped CP4.2 high-pressure pump, and the repair bill — injectors, lines, rails, pump — came in just under $12,000.

Here’s the part that still bothers me. The filters weren’t counterfeit. They weren’t even that badly made. They just skipped the one feature that matters on this engine: the hydrophobic water-separation screen inside the fuel filter. Without it, water passed straight through the media and hit the CP4.2, which has no lubrication film to spare and no filter downstream to catch anything.

The $46.99 filter kit didn’t save him money. It cost him a fuel system. And that’s the entire reason this guide exists.

Why the 2020-2025 L5P Is Different — and Why It Matters

GM redesigned the 6.6L Duramax for 2020 — the L5P generation — and it changed the filtration game in two ways most owners never notice.

First, the fuel filter moved. On the older LB7 through LML trucks, the fuel filter lived up top in the engine bay near the firewall. On the 2017-and-newer L5P, GM moved it underneath the truck — a cartridge-style element inside a plastic housing on the driver’s side frame rail, just in front of the fuel tank. The part number to remember is the TP1015, and it is now the only thing standing between whatever came out of your tank and the CP4.2 pump.

Second, the CP4.2 itself is the weak link. The Bosch CP4.2 high-pressure pump spins at over 20,000 psi and relies on the fuel itself for lubrication. It has no secondary filter downstream. Feed it water or grit, and the internal rollers scuff, shed metal, and send that metal through every injector in the rail. On a 2020-2025 truck, a “cheap” fuel filter isn’t a bargain — it’s a bet, and the downside is a five-figure rebuild.

The oil filter changed too. The PF26 is the updated spin-on canister for 2020+ (the 2017-2019 trucks used the PF2232), and it’s notable for one uncomfortable reason: among the big three diesel trucks, it’s the smallest oil filter. On an engine that holds 10 quarts, a smaller canister means less media area and less margin for a low-density aftermarket copy.

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

TP1015 — fuel filter (cartridge). This is the element that lives inside the plastic housing under the truck. It’s a cartridge, not a spin-on — you unscrew the 36mm cap, pull the old element, drop the new one in, and replace the O-rings. The factory spec calls for 5-micron media with roughly 98% water-separation efficiency, and the element is made by Mann+Hummel — the same company that builds the Wix WF10451, which is the same filter in a different box. The water-separation layer is the whole point. It’s the coalescing screen that stops emulsified water before it reaches the pump.

PF26 — oil filter (spin-on). A conventional spin-on canister with a silicone anti-drainback valve (instead of the older nitrile rubber), calibrated bypass valve, and synthetic-cellulose blend media sized for the L5P’s 10-quart sump and 7,500-mile intervals. It threads on the engine block the same way the old PF2232 did — but the internals are tuned differently, and that’s why the two part numbers aren’t interchangeable.

A3248C — engine air filter. The 2020+ trucks got a new airbox, and this is the panel filter that fits it. It’s a prism-shaped element that only goes in one way — three bottom slots and a top notch line it up — and the factory part is worth the extra money because the sealing edges compress against the lid for an airtight fit. A cheap replacement that doesn’t seal lets dust bypass straight into the turbo.

Note what’s not in this box: the CF185 cabin air filter. If cabin air quality matters to you, the four-filter kit adds it. This three-filter kit is the powertrain-protection core — intake, fuel, and oil.

What You Actually Pay: The Real Comparison

Here’s what these three filters cost from every major channel, verified September 2026.

The pattern is the same on every diesel platform: the white-label bundles undercut everyone by half, and they do it by deleting the specification. Doc’s Diesel publishes third-party test data — 3 microns at 98.13% on the fuel filter, 25 microns at 99% on the oil filter. ATRACYPART and RARAYC publish a marketing claim about “98% water capture” and nothing else. There is no industry-standard micron test for diesel fuel filters, which means the number on the box is often meaningless — but the water-separation screen is not. It either exists or it doesn’t, and that’s what cutaway testing separates the real filters from the knockoffs.

TruckTok’s $82.77 sits about 12% under Doc’s three-filter kit and roughly level with buying OEM separately — but you get all three in one box with part numbers that cross-reference to the factory spec.

What to Look For When Buying

1. Hydrophobic Water-Separation Coalescer: 

The TP1015 filter relies on a dual-stage coalescing screen to strip 98% or more of emulsified water out of diesel fuel. White-label knockoff filters often skip this internal screen entirely, passing water directly into the $2,000+ CP4.2 pump.

2. Correct Oil Filter Specification (PF26 vs PF2232):

2017 to 2019 L5P Duramax uses the PF2232.

2020 to 2025 L5P Duramax uses the PF26.

While both share identical mounting threads, the PF26 features an updated internal bypass valve spring calibration. Never trust a listing claiming one oil filter fits all 2017 to 2025 trucks.

3. Precision-Sealed Air Filter Housing: 

The 2020 and newer Duramax airbox requires a prism-shaped element with compliant perimeter foam. Rigid generic air filters fail to compress evenly against the airbox lid, allowing unmetered dirt bypass straight into the VGT turbocharger.

Installation: Three Filters, Three Locations

Step 1: Gather your tools

A 36mm socket (preferably six-point, so it doesn’t round the plastic cap — a 12-point works in a pinch; a 1-7/16" socket is a touch big but also fits), a ratchet with an extension, a pick or small screwdriver, shop rags, a drain pan, and clean diesel for lubing O-rings. For the oil filter, a strap wrench or cap wrench sized to the PF26. For the air filter, a flathead and Phillips screwdriver, plus an 8mm socket as a backup.

Step 2: Swap the fuel filter (under the truck)

The TP1015 lives in a plastic housing on the driver’s side frame rail, just in front of the fuel tank — crouch between the front and rear doors and look up. There’s a T40 drain plug in the cap — if the water-in-fuel warning is on, pull it to drain the water first; otherwise just put a drain pan under the housing, unscrew the 36mm cap, and pull the old cartridge. Wipe the housing out with a lint-free rag — you don’t want lint or debris in there. Replace both O-rings — the large one in the cap groove and the small one on the center stem (the pickup tube) — and lube each with clean diesel so it doesn’t roll or bind. The small stem O-ring is the one people miss; skip it and unfiltered fuel bypasses straight to the pump. Drop the new element in so it seats against the bottom, then thread the cap back on using the Mason twist: turn it left until you hear a click while pushing up, then tighten — that seats the threads before you apply torque so you don’t cross-thread the plastic cap. Torque the cap to the spec printed on it — “25 Nm + 5” means 25 Nm (18 ft-lb) plus 5 degrees of angle — and watch the gap between the cap and housing close as you go; the blue cap gasket should disappear from view when it’s seated. Don’t confuse foot-pounds with the drain plug’s inch-pounds, and don’t over-tighten; the plastic cap cracks.

Step 3: Swap the oil filter

The drain plug is a 15mm bolt — use a socket, not a crescent wrench or channel-locks, which will round the head off. Jack the front up a few inches if you need the clearance. Pull the drain plug and let it drain (10 quarts), then snug it back — tight enough to seal, but don’t overdo it or you’ll strip the threads. Spin the PF26 off the engine block and check the mounting face — the old seal often sticks to the block, and if you don’t pull it down you’ll double-seal and leak. Pre-fill the new filter with fresh oil (half a quart minimum, topping up as it soaks in), wet the gasket, and spin it on hand-tight, then just a touch more with the wrench. Add 10 quarts of 5W-40 full synthetic through a funnel, start it, and check for leaks. To reset the oil-life monitor, keep the engine running, tap the steering-wheel button, scroll to Oil Life, push straight in, and confirm the reset to 100%.

Step 4: Swap the air filter

Pop the hood, disconnect the MAP sensor first — push the red safety clip back, then push the tab down and pull the connector straight back; don’t yank the wiring. Loosen the hose clamp and remove the six 8mm screws (a Phillips screwdriver works too), then pull the lid straight back. Vacuum out any dirt in the airbox with a shop vac before dropping the new element in. The A3248C is prism-shaped, so note which way the old one came out — three bottom slots and a top notch only line up one way — and set the new one flush on all four corners. Reinstall the lid and snug the six screws to just 35 inch-pounds — almost nothing; over-tightening cracks the plastic. Reseat the hose on its lip and clip the connector back on. To reset the air-filter life monitor, start the engine, toggle to the air-filter screen, and hold the enter button to reset it to 100%.

Step 5: Prime the fuel system

Keep your foot off the brake, press and hold the start button until the dash lights up (accessory mode), and let it sit while the in-tank lift pump primes the system — you’ll hear the pump run, then air bubbling back to the tank. Repeat the cycle a few times until you no longer hear the air, then shut it off, wait a few seconds, and start the truck. If it doesn’t fire, keep priming — it sometimes takes two or three tries. Don’t crank the engine until the system is primed; the CP4.2 does not like being fed air. Start it, let it idle, and check all three locations for leaks.

Five Expensive Mistakes

Mistake #1: Buying the PF2232 for a 2020+ truck

The PF2232 fits the 2017-2019 L5P; the 2020+ uses the PF26. They thread on the same, but the bypass valve calibration is different. A seller who lists “PF2232/PF26” as if they’re one part is how you end up with the wrong calibration.

Mistake #2: Reusing the fuel-filter O-rings

The TP1015 kit comes with two fresh O-rings for a reason. Reusing the old ones is the number-one cause of post-service fuel leaks — and a fuel leak on a 20,000-psi system is not a drip you want to discover at speed.

Mistake #3: Skipping the prime after a fuel-filter change

Cranking the engine on an unprimed system sends air through the CP4.2, which relies on fuel for lubrication. On these push-button trucks, hold the start button (foot off the brake) and let the lift pump prime for two full minutes before you start it. A couple extra minutes of priming is free; a pump is not.

Mistake #4: Gambling on a $46 white-label kit

The $46 bundle skips the water-separation screen and the micron spec. On an engine where the fuel filter is the only barrier before a five-figure pump, that’s not saving money — it’s deferring a much bigger bill.

Mistake #5: Stretching the interval on a small oil filter

The PF26 is the smallest oil filter of the big three, and it has less margin for a stretched interval. Run it to 7,500 miles with a quality full synthetic, and don’t push past that on a truck that tows.

Frequently Asked Questions

What’s the difference between this 3-filter kit and the 4-filter kit?

This kit omits the CF185 cabin air filter. If cabin air quality matters — dusty, high-pollen, or heavy-traffic driving — step up to the four-filter kit. This three-filter kit covers the powertrain core: fuel, oil, and engine air.

Is the TP1015 a spin-on or a cartridge?

Cartridge. The element lives inside a plastic housing under the truck, and you unscrew the 36mm cap, swap the element, and replace the O-rings. You don’t throw the whole housing away.

Are the PF26 and PF2232 interchangeable?

Not really. They thread on the same, but the bypass valve calibration is different. 2020+ uses the PF26; 2017-2019 uses the PF2232. Use the one your year calls for.

Can I use 2017-2019 filters on a 2020+ truck?

Only the TP1015 fuel filter carries over (it fits 2017-2026). The oil filter changed to the PF26 for 2020+, and the airbox changed so the A3248C doesn’t fit the older trucks. Don’t mix years.

Can I install these myself?

Yes. The fuel filter is the only part that surprises people — it’s under the truck, not in the engine bay. The whole job is drain, swap, re-prime, and figure an afternoon in the driveway.

How do I prime the fuel system after a change?

On 2020+ push-button trucks, keep your foot OFF the brake pedal, press and hold the Start button for ~5 seconds until the instrument cluster illuminates (Service/Accessory Mode). The in-tank lift pump will run for 15–20 seconds to purge air. Cycle the ignition OFF, and repeat this process 3 to 5 times until air bubbling sounds inside the fuel tank fade out completely, then start the truck.

How often should I change each filter?

Fuel filter every 15,000 miles (10,000 under severe duty), oil filter at every oil change (7,500 miles), and the air filter every 15,000-20,000 miles. This kit lines up with the 15,000-mile major service. Owners who cut the filter open at 10,000 miles routinely find it still clean, while those who push past 17,000 usually find it visibly dirty — so 15,000 is the sweet spot. Plenty change early anyway, because the TP1015 is cheap insurance against a five-figure pump.

Why is the CP4.2 pump such a big deal?

It’s a high-pressure pump with no downstream filter that relies on fuel for lubrication. Feed it water or grit and it sheds metal into every injector. The repair is routinely a five-figure job, which is why the fuel filter is the one place you don’t cut corners.

Why is the $46 white-label kit so cheap?

Because it deletes the specification — and usually the water-separation screen. There’s no published micron rating, no test data, and a cutaway often reveals the hydrophobic screen is missing entirely. That’s how it hits $46.

What oil should I run in a 2020-2025 L5P?

GM specifies a 5W-40 full synthetic for the L5P (the earlier trucks used 15W-40 conventional). The 10-quart sump and the small PF26 filter mean you want a quality full synthetic and a 7,500-mile interval.

Why is the PF26 so small?

It’s just how GM packaged the L5P — the Duramax oil filter is the smallest of the big three diesel trucks. That’s not a defect, but it does mean you have less margin for a low-density aftermarket filter.

Does this kit include the cabin filter?

No. The CF185 cabin filter is in the four-filter kit. If you want cabin coverage, either add the air-and-cabin combo or grab the full kit.

Should I upgrade to a billet aluminum filter housing?

The factory TP1015 housing is plastic, and it’s the part most likely to crack or round off over repeated filter changes — especially if you over-torque it. A billet 6061 aluminum housing is a direct replacement that threads on the same, and the better ones add a drain nipple so you can empty the housing cleanly next time instead of spilling fuel down your arm. It’s not required, and it doesn’t change the filter interval — but if you’re keeping the truck long-term and doing this job yourself, it’s a one-time upgrade that makes every future change cleaner.

What does a dealer charge to change this fuel filter?

Dealers and quick-lube shops routinely quote $140–$180 just to swap the fuel filter — a 15-minute job with a ~$60 filter. Doing it yourself costs the filter plus a 36mm socket, and you’re done in about 15 minutes. It’s one of the easiest DIY jobs on the L5P, and the savings add up fast when you do it every 15,000 miles.

Get All Three Filters, in One Box

If your 2020-2025 Duramax has been running on a mix of “whatever was on sale” filters, this kit closes the gap. One order puts the TP1015 fuel filter, PF26 oil filter, and A3248C air filter in a single box — matched to the truck, OEM-spec, and ready for one afternoon in the garage.

Get the 2020-2025 Duramax L5P 3-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

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.