Disclosure: As an Amazon Associate, we earn from qualifying purchases. If you click a link on this page and make a purchase, we may receive a small commission at no extra cost to you.
Oil mist from the crankcase ventilation system can move into your truck’s intake tract, where it may contribute to residue over time. The K&N 81-0800 Air Oil Separator is a vehicle-specific catch can designed to intercept that oil before it reaches the intake. Its 6-ounce reservoir, factory-style connectors, and tool-free reservoir access are practical strengths. The main tradeoffs are strict engine fitment, possible battery-tray drilling, routine servicing, and a California sales-and-use restriction.
Quick Verdict
Editorial Rating: 8.4/10, Recommended with caveats
Best For: Owners of supported Ford F-150, F-150 Raptor, and Expedition engine applications who want a direct-fit, serviceable oil separator.
Bottom Line: The K&N 81-0800 offers a cleaner, more application-specific setup than many universal catch cans. Buy it only after confirming the exact year, engine, emissions rules, and installation requirements for your vehicle.
| Specification | Verified Detail |
|---|---|
| Brand | K&N |
| Model / part number | 81-0800 |
| Product type | Vehicle-specific air oil separator / oil catch can |
| F-150 engine applications in K&N manual | 2011-2023 3.5L EcoBoost; 2015-2021 2.7L EcoBoost; 2011-2023 5.0L |
| Additional application in K&N manual | 2018-2021 Ford Expedition 3.5L EcoBoost |
| Amazon-listed Raptor range | 2017-2023 Ford F-150 Raptor; verify the engine and exact application before ordering |
| Reservoir capacity | 6 fluid ounces |
| Catch can size in parts list | 2.5-inch outside diameter x 4.5 inches high |
| Product box dimensions | 13.38 x 7 x 3.13 inches |
| Weight | 2.5 pounds |
| Connections | OEM-style quick-connect fittings and robust hoses |
| Included hardware | Catch can, fittings, 20-inch and 12-inch hoses, mounting bracket, bolts, washers, nuts, and screws |
| Installation time | About 20 to 30 minutes, according to K&N |
| Tools listed by K&N | Drill, 1/4-inch drill bit, 10 mm wrench, 10 mm socket, 3/32-inch Allen key, and adjustable wrench |
| Inspection interval | Check every 10,000 miles or 12 months, sooner for towing, off-road use, or other harsh conditions |
| Warranty | K&N No-Hassle Lifetime Limited Warranty, subject to current terms |
| California restriction | Not legal for sale or use in California on a pollution-controlled motor vehicle |
What Is the K&N 81-0800 Air Oil Separator?
The K&N 81-0800 is a vehicle-specific air oil separator that replaces part of the factory positive crankcase ventilation line on supported Ford engines. Blowby can carry oil mist through that line. The separator routes the vapor through a reservoir so suspended oil can collect before the remaining gas continues toward the intake.
K&N built this kit around a 6-ounce reservoir, application-specific bracket, two hoses, and factory-style quick-connect fittings. The reservoir can be checked and emptied without tools after installation. That service design is useful because a catch can only works as intended when you inspect it and keep the collected fluid below its working limit.
This is a preventive add-on, not a repair. It does not clean existing intake deposits, repair a faulty PCV system, stop excessive blowby from worn engine parts, or guarantee a horsepower increase.
Who Should Buy It?
Best For
- Owners with an exact year-and-engine application listed by K&N.
- Drivers who tow, go off-road, or keep their truck long enough to value preventive intake care.
- DIY owners who want factory-style connectors and are comfortable drilling and routing hoses when required.
Skip If
- Your year, engine, or vehicle configuration is not confirmed by K&N.
- Your vehicle is a California pollution-controlled motor vehicle.
- You want a maintenance-free part or do not want to drill the battery tray if your application requires it.
Before You Buy: Do not rely on the broad F-150 year range alone. Match part 81-0800 to your exact engine, model year, emissions location, and installation sheet. The K&N manual lists specific engine ranges, and some installations require holes to be drilled in the battery tray.
Fit and Compatibility
The fitment details are more specific than the product’s short marketing title. K&N’s installation sheet lists 2011-2023 F-150 3.5L EcoBoost, 2015-2021 F-150 2.7L EcoBoost, 2011-2023 F-150 5.0L, and 2018-2021 Expedition 3.5L EcoBoost applications. The Amazon title also identifies 2017-2023 F-150 Raptor compatibility, but you should still verify the exact engine and configuration.
Do not assume the kit fits PowerBoost, right-hand-drive, newer model years, or another Ford engine unless K&N’s current part finder confirms it. Aftermarket intake parts, relocated batteries, auxiliary wiring, or other under-hood modifications can also affect bracket clearance and hose routing.
Materials and Build Quality
K&N describes the kit as using premium OEM-style connectors and robust hoses. The manual shows a dedicated metal mounting bracket, threaded fittings, two pre-sized hoses, locking hardware, and an application-specific can. This is a more organized package than a universal can that requires you to source hoses, adapters, and a mounting point separately.
The 6-ounce reservoir offers useful collection capacity without turning the kit into a large engine-bay assembly. However, capacity does not remove the need for checks. Fluid accumulation changes with engine condition, temperature, trip length, towing, and off-road use.
How It Handles Blowby and Intake Contamination
K&N says the separator is designed to capture oil carried by blowby and reduce oil and contaminant buildup in the intake tract. That is the correct reason to buy this part. It is not a power adder, and you should not expect a clear seat-of-the-pants performance change after installation.
The likely benefit is easier long-term control of oil mist entering the intake. The amount collected will vary. A nearly empty can does not automatically mean the product is defective, and a can that fills quickly may justify checking the engine and PCV system rather than simply emptying it more often.
Installation and Setup
K&N rates installation at about 20 to 30 minutes, but the job is more involved than snapping two hoses together. The official tool list includes a drill, 1/4-inch drill bit, 10 mm wrench, 10 mm socket, 3/32-inch Allen key, and adjustable wrench. The bracket position changes by engine, and the manual instructs installers to drill the battery tray on several applications unless a suitable existing hole is present.
After mounting the bracket and can, you remove the factory PCV line, install the fittings, and connect the two supplied hoses. K&N recommends PTFE tape on the fittings for a proper seal. Hose direction matters: the hose with the straight fitting goes to the intake manifold, while the hose with the 45-degree fitting goes to the PCV valve.
Setup Tips Before First Use
- Let the engine cool and disconnect or protect nearby electrical components before drilling.
- Confirm the bracket location for your engine before marking any holes.
- Keep metal shavings away from the battery, wiring, intake openings, and moving parts.
- Seat every quick connector fully and route hoses away from heat, sharp edges, belts, and fans.
- Start the engine and listen for a vacuum leak, then inspect the fittings again after a short drive.
Pro Tip: Photograph the factory PCV routing before removal and label the two new hoses. This makes it easier to confirm that the straight fitting reaches the intake manifold and the 45-degree fitting reaches the PCV valve.
Maintenance and Long-Term Use
K&N recommends checking the separator every 10,000 miles or 12 months, whichever comes first. The manual calls for earlier checks when the vehicle is used in harsher conditions such as towing or off-road driving. A new installation is also worth checking after the first few drives so you can confirm the fittings remain seated and learn how quickly your engine produces condensate and oil.
The reservoir can be checked and emptied without tools, which lowers the effort of routine service. Empty it safely with the engine cool, dispose of the collected fluid according to local rules, and inspect the hoses for soft spots, cracks, rubbing, or oil seepage.
Do not let the separator become a substitute for oil changes, PCV inspection, or diagnosis. If it collects an unusual amount of oil, the truck develops a vacuum-related fault, or you notice smoke, leaks, or rough running, have the system checked by a qualified technician.
How It Performs in Real Use
For Daily Driving
During ordinary commuting, the separator works quietly in the background. You may not feel a change from the driver’s seat. The practical measure is whether it collects fluid while the hoses, fittings, and engine operation remain normal.
For Higher-Mileage Trucks
A higher-mileage engine may send more oil mist through the PCV path, but collection alone does not diagnose engine wear. The K&N can may reduce how much oil reaches the intake, yet it cannot correct worn rings, a damaged turbocharger, a restricted PCV valve, or existing carbon deposits.
For Towing and Off-Road Use
K&N specifically recommends checking the can sooner under harsher use, including towing and off-road driving. Those owners should establish a shorter inspection routine rather than waiting automatically for the 10,000-mile or 12-month maximum interval.
For Long-Term Ownership
The strongest case for this kit is preventive maintenance on a vehicle you plan to keep. Its direct-fit hoses and tool-free reservoir access make ongoing service easier than many improvised universal installations, provided the exact application fits and you maintain it.
Common Mistakes to Avoid
- Buying by model name without checking the engine and year range.
- Calling the 13.38 x 7 x 3.13-inch box dimensions the installed can dimensions.
- Assuming the installation never requires drilling.
- Reversing the straight and 45-degree hose connections.
- Routing a hose against a sharp edge, hot component, belt, or fan.
- Ignoring the reservoir because the truck still runs normally.
- Using the separator to mask excessive oil use, smoke, or another mechanical problem.
Compatibility and Safety Notes
K&N states that part 81-0800 is not legal for sale or use in California on a pollution-controlled motor vehicle. That is a major buying limitation, not a minor disclaimer. Check the current manufacturer page and your local emissions rules before ordering or installing any crankcase ventilation modification.
Drilling near a battery tray requires care. Protect the battery and wiring, control metal shavings, wear eye protection, and do not drill until the bracket position matches the instructions for your engine. A professional installation is the safer choice if you are not comfortable modifying the tray or verifying PCV routing.
Keep the purchase record, installation instructions, and photos of the finished routing. An aftermarket part does not repair unrelated faults, and coverage questions can depend on the cause of a failure and the terms of the applicable warranty.
Pros and Cons
Pros
- Vehicle-specific bracket, hoses, and quick-connect fittings.
- 6-ounce reservoir with tool-free checking and emptying.
- Supports several F-150 EcoBoost and 5.0L model-year ranges.
- Clear hose-routing instructions for the PCV and intake connections.
- No-Hassle Lifetime Limited Warranty from K&N, subject to current terms.
Cons
- Some applications require drilling holes in the battery tray.
- Fitment is engine-specific and does not cover every F-150 configuration.
- Not legal for sale or use in California on pollution-controlled motor vehicles.
Is It Worth the Price?
The K&N 81-0800 sits in the mid-range to premium part of the catch-can market. Its value comes from the application-specific bracket, pre-sized hoses, quick-connect fittings, 6-ounce capacity, and easier reservoir service. Those features can save planning time compared with a basic universal can.
It is worth considering when your vehicle is a confirmed fit and you plan to maintain the separator. It is not the best value if your application needs custom work, you live in California, or you want a no-service modification.
How It Compares to Alternatives
A universal catch can may cost less and fit more vehicles, but you usually need to choose the mounting point, hose sizes, adapters, and routing yourself. The K&N kit makes more sense when you value a direct-fit package and a clear application-specific manual.
J&L offers direct-fit single-can separators for many F-150 engines, while Mishimoto sells engine-specific systems that may use larger or dual reservoirs on selected model years. Compare exact engine coverage, reservoir layout, mounting method, service access, emissions restrictions, and installation difficulty before choosing among them.
Warranty and Support
K&N lists a No-Hassle Lifetime Limited Warranty for the 81-0800. Warranty protection is subject to the manufacturer’s current conditions, purchase channel, proof-of-purchase rules, and exclusions, so keep your receipt and review the live terms before relying on coverage.
The official product page also provides the installation sheet and K&N technical-support information. Use the manual for the installation sequence rather than depending only on a retailer description or customer photo.
Frequently Asked Questions
What does the K&N 81-0800 Air Oil Separator do?
It routes crankcase vapor through a 6-ounce reservoir so suspended oil can collect before the gas continues toward the intake. It is designed to reduce oil contamination in the intake tract, not to add guaranteed horsepower.
Which F-150 engines are listed in the K&N manual?
The manual lists 2011-2023 3.5L EcoBoost, 2015-2021 2.7L EcoBoost, and 2011-2023 5.0L F-150 applications. It also lists the 2018-2021 Expedition 3.5L EcoBoost.
Does it fit every 2017-2023 F-150 Raptor?
The Amazon title lists 2017-2023 Raptor compatibility, but broad model-year wording is not enough for a safe purchase. Confirm part 81-0800 against your exact engine and vehicle in K&N’s current fitment system.
Does installation require drilling?
It can. The K&N instructions tell installers to use the bracket as a template and drill 1/4-inch holes in the battery tray for several engine applications, although some later vehicles may have an existing usable hole.
How often should you check and empty it?
K&N recommends checking it every 10,000 miles or 12 months. Check it sooner if you tow, drive off-road, operate in harsh conditions, or are still learning how quickly your engine fills the reservoir.
Is the K&N 81-0800 legal in California?
K&N states that it is not legal for sale or use in California on a pollution-controlled motor vehicle. Review the current manufacturer notice and local rules before purchase or installation.
Will it clean existing deposits or fix excessive oil use?
No. It may reduce additional oil mist entering the intake, but it does not remove old deposits or repair worn rings, turbocharger faults, PCV problems, leaks, smoke, or excessive oil consumption.
Who should skip this oil separator?
Skip it if K&N does not confirm your exact application, you cannot legally use it where the vehicle is registered, or you want a maintenance-free part. You should also use a professional installer if drilling and PCV hose routing are outside your skill level.
The Bottom Line
The K&N 81-0800 is a well-organized direct-fit oil separator for its supported Ford applications, with a 6-ounce reservoir, factory-style connections, and convenient tool-free servicing. It is a good choice for owners who will verify fitment and maintain it, but you should skip it if your engine is not listed, California rules apply, or you do not want an installation that may require drilling.
Ready to Buy?
Confirm your exact engine, model year, installation requirements, and local emissions rules before ordering.
