Fleet · Bypass Oil Filtration
Bypass Oil Filter for Semi Trucks — When It Pays & What to Run
A bypass oil filter is a kidney loop for your engine oil. It takes a small, steady stream off a pressurized oil port, runs it through media fine enough to catch soot and particles the full-flow filter lets through, and returns it to the sump. Clean oil lasts longer and wears the engine less. On a Class 8 tractor-trailer it earns its keep when the truck idles a lot, works dirty, or runs long drains on oil analysis.
Last reviewed: October 2026 · Based on AMSOIL bypass filter data sheet G498 and the AMSOIL Bypass Filtration Update of October 13, 2026 · Written by a Red Seal 310T truck and coach technician
A bypass oil filter cleans a small share of the oil, all the time, down to 2 microns. It works alongside the full-flow filter, never in place of it. Update, October 2026: AMSOIL has discontinued its heavy-duty and universal bypass kits (Dual-Gard BMK22, BMK21, BMK23, BMK30) and the EaBP100, EaBP110 and EaBP120 filters. The EaBP90 returns by the end of 2026 as AMSOIL's only bypass filter. For a Class 8 truck today, the Red Seal tech pick is a quality full-flow filter plus oil analysis at every change, which also tells you whether bypass would pay.
EaBP Filters
600 h / 2 yr
Universal Kits Retired
Back in Stock
What Does a Bypass Oil Filter Do?
The full-flow filter has to pass all the oil the pump moves, so its media can only be so fine. A bypass filter only sees a small stream, so it can use much denser media that holds soot and fine wear particles. It works alongside the full-flow filter, never in place of it.
Full-Flow Filter
- → Sees 100% of the oil on its way to the bearings
- → Coarser media so it never starves the engine
- → Required on every engine
Bypass Filter
- ✓ A small stream off a pressurized port, back to the sump
- ✓ 2-micron media that holds soot and fine wear metal
- ✓ Keeps polishing the oil every minute the engine runs
Check your engine first. Many Class 8 engines already carry a bypass element from the factory. Some Volvo D13 setups, for example, run three oil filters instead of two, and the third is a bypass. If yours has one, an add-on kit is extra capacity and extra filtration, not a first line of defence.
When Does Bypass Filtration Pay Off on a Semi?
Modern OEM drain intervals already run 35,000 to 75,000 miles, so on a clean highway tractor a bypass kit pays back slowly. It pays fastest where soot, dirt and idle hours load the oil before the miles do, and on trucks running long drains on oil analysis.
High Idle Time
Idle hours build soot and fuel in the oil without adding miles. The bypass keeps soot in check between changes.
Vocational & Dusty Work
Dump trucks, logging, construction and gravel roads put more fine dirt in the oil than highway miles do.
Long Drains on Oil Analysis
Cleaner oil holds viscosity and TBN longer, and the reports show it.
Older, Higher-Mileage Engines
More blow-by means more soot. A bypass buys margin on an engine you want to keep running.
Best Bypass Oil Filter for a Class 8 Truck: AMSOIL's October 2026 Update
On October 13, 2026, AMSOIL announced it is consolidating its bypass filtration line around the turbodiesel pickup market. The Dual-Gard (BMK22), Single-Remote (BMK21), Universal Dual-Remote (BMK23) and Heavy-Duty (BMK30) kits are discontinued, along with the EaBP100, EaBP110 and EaBP120 filters. AMSOIL says more news is coming later this fall. Until a heavy-duty option is back, here's what a Red Seal tech recommends for a Class 8 truck.
- Shows soot, wear metals and oil life
- Tells you whether bypass would actually pay on your truck
- The proof behind any drain past the OEM interval
- Many Class 8 engines already carry a factory bypass element
- Replace every filter in the system at each oil change
- Let the reports, not the calendar, decide any extension
- Oil and analysis kits at commercial pricing
- Shipped straight to your shop or yard
- Reports reviewed with a Red Seal tech
Replacement Filters for AMSOIL Bypass Kits
If you already run an AMSOIL bypass kit, it still works. Here's what AMSOIL says to use now for each filter. Replacement parts are available while supplies last, and the AMSOIL Bypass Filter Systems warranty is unchanged.
| Filter (Kit) | Status | What to Use Now |
|---|---|---|
| EaBP120 (BMK30 Heavy-Duty) | Discontinued | Donaldson P570027 (AMSOIL's listed replacement) |
| EaBP110 (used on the BMK22 Dual-Gard) | Discontinued | Remaining stock while it lasts; AMSOIL says alternative sources will be announced |
| EaBP100 (7.5″) | Discontinued | Remaining stock while it lasts; alternatives to be announced |
| EaBP90 (6″) | Retooling, back by end of 2026 | WIX WL11042 until then (AMSOIL's recommendation) |
When the EaBP90 returns, it will be AMSOIL's only bypass filter, rated for 60,000 miles (96,561 km), 600 hours or two years, whichever comes first. Pickup kits for the GM 6.6L, Ford 6.7L and Cummins 5.9/6.7L are getting updates AMSOIL plans to announce later this year.
When Do You Change a Bypass Filter?
Once a year, or sooner if a report says so. If you care enough to run bypass filtration, you're already doing oil analysis, or you should be. The reports show when the filters are loaded, and they're the only safe way to stretch an oil change past the engine maker's interval.
Sample Every Change
Build a baseline before the kit goes on, then keep sampling after.
Watch Soot & Particles
When soot or wear metals start climbing between changes, the bypass filters are full.
Extend on Data
Step the oil change out only on clean reports, within AMSOIL's 60,000 mi / 600 h / 1 yr oil cap unless analysis supports more.
Send me your reports and we'll set each truck's interval on its own data. Call 888-490-0074 (toll-free)