The Complete Guide to AMSOIL Bypass Oil Filtration
Engine wear is a particle-size problem. Decades of SAE research, AMSOIL field testing, and used-oil analysis from fleets all point to the same conclusion: the majority of measurable bearing, cam, ring, and cylinder wear comes from particles between 5 and 30 microns in size — particles smaller than the human eye can see, suspended invisibly in your oil. The factory full-flow oil filter on your engine is simply not engineered to capture those particles efficiently. It is engineered to flow huge volumes of oil at low pressure drop, and to never starve the bearings. That trade-off — flow over efficiency — is why a bypass oil filter exists.
How a Bypass Oil Filter Works
An AMSOIL bypass system installs in parallel with your factory full-flow filter. It taps a pressurized oil port (or, on dual-remote systems, the spin-on filter mount itself), routes a small percentage — about 5% — of pump flow through a dense synthetic-media bypass element, and returns the cleaned oil to the oil pan. The bypass filter does not need to support full bearing-feed pressure, so it can be made far more restrictive and far more efficient than any full-flow filter. AMSOIL bypass elements remove contaminants down to 2 microns. Run continuously, the bypass cleans the entire sump until the engine is operating on what oil analysts call analytically clean oil.
Single-Remote vs. Dual-Remote — Same Filtration, Different Packaging
AMSOIL builds two bypass system architectures. A single-remote system (BMK21 universal, BMK31 / BMK32 / BMK33 / BMK34 engine-specific) leaves your factory full-flow filter in its OEM location and only mounts the bypass filter remotely. It takes less under-hood real estate and is the easier install on tightly packaged late-model diesel pickups. A dual-remote system (BMK22 DUAL-GARD, BMK23 universal, BMK26 / BMK27 / BMK28 engine-specific) relocates both filters to a single mount in your engine bay — easier serviceability, easier filter visibility, and a small bonus in oil capacity that helps cooling and stretches drain intervals further. Filtration efficiency is identical between architectures; pick whichever fits your truck and your wrench preferences.
Engine-Specific Kits — Power Stroke, Cummins, Duramax
The most popular AMSOIL bypass installs are on diesel pickups — the Cummins 5.9L / 6.7L (BMK34), Ford 6.0L / 6.4L Power Stroke (BMK31), Ford 6.7L Power Stroke (BMK33 / BMK28), Ford 7.3L Power Stroke (BMK26), and GM 6.6L Duramax (BMK32 / BMK27). Engine-specific kits ship with the correct adapters, bracket, hose lengths, and pressure ports already sized for that platform. No improvising fittings, no guessing on hose routing, no clearance fights with the turbo or exhaust. For applications without a dedicated kit — including gas engines, classics, and custom builds — the universal BMK21 (single) and BMK23 / BMK22 DUAL-GARD (dual) kits work with any pressurized oil port.
Heavy-Duty BMK30 — Class 8, Marine, Industrial, Agriculture
The AMSOIL Heavy-Duty Bypass System (BMK30) is built for over-the-road Class 8 trucks, marine diesels, agricultural tractors, construction equipment, and stationary industrial engines. Larger filter capacity, larger hoses, and heavier brackets handle the vibration and duty-cycle severity these applications throw at a bypass system. Paired with AMSOIL synthetic oil and an oil-analysis program, BMK30 is the foundation of fleet drain-interval extension that has paid for itself many times over for AMSOIL commercial accounts.
Soot — Why Diesel Owners Love Bypass Filtration
Modern emissions-controlled diesels generate soot. EGR routes a measured fraction of exhaust back into the intake, and a portion of that soot ends up in the oil. Soot particles are typically well under 2 microns — invisible to a full-flow filter — and as soot loads up, oil viscosity climbs, abrasive wear increases, and oil drain intervals get shorter. AMSOIL bypass systems are one of the only practical ways to actively pull soot out of the oil between drains, which is exactly why diesel pickup forums treat the BMK kits as nearly mandatory hardware on a 6.0L, 6.4L, 6.7L, or Duramax.
Pair the System With AMSOIL Ea Full-Flow Filters and Synthetic Oil
A bypass filter only works as well as the rest of your filtration and lubrication system. AMSOIL Ea full-flow oil filters use synthetic nanofiber media to deliver 98.7% filtration efficiency at 20 microns — far above any cellulose-paper filter — and are rated for up to 25,000 miles or 1 year of service when paired with AMSOIL Signature Series synthetic motor oil. Use the Ea filter as your primary, the EaBP element in the bypass, and AMSOIL synthetic oil in the sump, and you have the most effective consumer-grade engine-protection package on the market.
Order Direct From an Independent AMSOIL Dealer
Every product on this page links directly to AMSOIL.com with our dealer code attached. Order at retail, or enroll free in the Preferred Customer program to save 25% on every order with no minimums. Fast shipping from regional warehouses across North America. Need help spec'ing the right kit for your truck or fleet? Contact us — we'll match you to the exact AMSOIL bypass system, full-flow filter, and Signature Series oil package for your application.
