AMSOIL By-Pass Filters

A Little History, What Are They And Should My Vehicle(s) Have One?

Oil filters have been included on automobile and truck engines for decades but it wasn’t always that way. Originally, engines didn’t have oil filters or, if they did, it was a simple screen placed at the oil pump intake . It wasn’t until 1923 when Ernest Sweetland and George Greenhalgh were granted a patent for the “Pure Oil Later” or “Purolator” filter that you could purchase a vehicle with a full pressure lubrication system.

This system however was a By-Pass System, not the full flow oil filter seen today. Most of the oil was pumped, unfiltered, to the engine with a small percentage of the oil being pumped through the filter.

It was many years later that full flow oil filters became standard equipment and these first full flow filters were cartridge filters, similar to what is making a comeback now. Still later the spin-on full flow oil filter became a standard in the industry. (I had a 1959 Rambler American and a 1964 Chevrolet Impala 283 that came through with cartridge filters.)

What Is The Difference Between A Full Flow And A By-Pass Filter?
Picture of AMSOIL Full Flow Filter

Full Flow Filters: With the full flow filter system, all of the oil goes through the oil pump to the oil filter and then to the engine components1. While this type of system insures that the oil is filtered before reaching cams, lifters, valves etc., it is a compromise filter system. Why? Because filtration is a compromise. You can either have very good oil flow or very good oil filtration, but not both.

Because the oil not only lubricates but also provides a large percentage of the cooling, the engine requires a significant oil flow to keep working properly. To achieve that flow, the filter media cannot be too restrictive.

Most full flow filters do a reasonable job of filtering the oil of particles down to the 20 to 40 micron range. (Note: Don’t compare filter micron ratings unless they give you a percentage rating too. To say a filter has a “X” micron rating doesn’t tell you anything. Does it remove all of the particles “X” microns and larger or does it remove 5% of the particles “X” microns and larger? You don’t know and it is a BIG difference. A screen door can remove 10 micron particles but you wouldn’t use that material to filter your oil. If they say “Nominal” rating it usually means 50%. AMSOIL Full Flow filters have a 98.7% efficiency rating (which the industry considers absolute) at 20 microns. Nothing 20 microns or larger gets through the filter.)

The problem is that most engine wear is caused by particles in the 5 to 40 micron range. Particles smaller than 5 microns (0.00019 inches) are usually smaller than the spaces between moving components so even if they get between moving parts, they cause little to no wear. Particles larger than 40 microns (0.0016 inches) are getting to be larger than the clearances between parts so they aren’t as likely to get into the lubrication boundary between parts.

So, you can see that even if you are using a very good full flow filter, a lot of wear causing particles will go unfiltered. This is especially true for diesel engines which accumulate a lot of “Soot” in the oil. While the soot particles are small, sub-micron in size to start, as they accumulate in the oil they begin to bind together causing larger and larger particles that are very abrasive. Once they get up to 5 microns and larger in size, they really start to cause wear.

AMSOIL By-Pass Filter Element

By-Pass Filters: By-Pass Filters are just that, filters that take a small percentage of the oil being pumped and do a really good job of cleaning it up. The AMSOIL By-Pass Filters take about 10% of the oil that is being pumped and remove 98.7% (absolute) of the particles 2 microns (0.00008 inches) and larger. This means that any wear causing particles that made it through the full flow filter are removed by the AMSOIL By-Pass Filter.

Be advised that By-Pass Filters work in conjunction with Full Flow Filters. You can operate your vehicle with its Full Flow Filter and without a By-Pass Filter but not the other way around. A By-Pass filter alone doesn’t flow enough oil to provide proper lubrication and cooling.

What are the benefits of AMSOIL By-Pass Filtration?

  • Efficient small-particle and soot removal.
  • Equipment constantly runs on clean oil.
  • Increased engine efficiency.
  • Can significantly extend engine.
  • Can significantly extend turbo-charger life.
  • Increased filtration capacity and life.
  • Improved oil cooling.
  • Increased fluid system capacity.
  • Dramatically extended drain intervals.

Who will benefit using AMSOIL By-Pass Filtration?

  • Owners of light and heavy duty diesel engines.
  • Owners of any turbocharged vehicle (gasoline or diesel).
  • Owners of fleets.
  • Owners who do a lot of miles (in excess of 20,000 per year) and plan on keeping vehicles well past 100,000 miles.
  • Owners who regularly work their vehicles or equipment hard.
  • Owners who just want the best for their vehicles or equipment.

Which AMSOIL By-Pass System is right for me?

It all depends on your application. For most gasoline and diesel vehicle and light truck applications, AMSOIL has several options. The simplest is usually the dual remote system which has an adapter that fits where the current full flow filter mounts and a mount that holds both the full flow and By-Pass filters. This not only places both filters in one location which can make for quicker, easier changes, in some cases it allows for the use of a larger full flow filter which increases oil capacity. It also returns the oil from the By-Pass filter directly into the oil stream coming out of the full flow filter going to the engine components. If you prefer to leave the full flow filter on the OEM mount, AMSOIL offers the Universal Single Remote By-Pass Mount that holds only the By-Pass Filter. Even the smallest By-Pass Filter will increase your oil capacity by 1 quart.

NOTE: Before purchasing any of these systems at the prices shown, check with us and we will tell you how to get a better price. (No pressure, just information.)

Also, one of the advantages if using a By-Pass system is that you no longer change oil on a time or mileage schedule but use oil analysis to determine when it is time to change the oil. Oil analysis provides information on wear metals, contamination, the oils additive package and whether the oil is fine for continued use or should be changed. The easiest way to get the oil sample is by using a petcock valve. Check the “Installation & Servicing Instructions” for the By-Pass System you choose to see information on the appropriate petcock valve and any required fittings. You can order the parts from AMSOIL or they are usually available at any local hardware or plumbing supply house that carries brass fittings.

Universal Single & Dual Remote By-Pass Filter Systems.

AMSOIL's Universal Single Remote By-Pass System

The Universal Single Remote By-Pass System (BMK21)
The Universal Single-Remote Bypass System provides superior filtration performance while working in conjunction with the engine’s full-flow oil filter. This system connects to the engine through a pressurized oil port. System includes mount, mounting hardware, hose and hose fittings. Note: The EaBP bypass oil filter is sold separately. EaBP120 will not work with this system.

BMK21 Installation & Servicing Instructions


AMSOIL Universal Dual Remote By-Pass Filter System (BMK23)

The Universal Dual Remote By-Pass Filter System (BMK23)
The Universal Dual Remote Bypass provides superior filtration performance by combining the full-flow and bypass filters on a single mount. System includes mount, mounting hardware, hose and hose fittings. Note: The spin-on adapter, EaO26 full-flow oil filter, and a Bypass oil filter are each sold separately. EaBP120 will not work with this system. You must purchase the spin-on adapter that matches the filter thread size on your vehicle. Contact us or AMSOIL Tech Support for info on the proper adapter for your application.

BMK23 Installation & Servicing Instructions

Diesel Applications

Cummins 5.0L / 5.9L / 6.7L Diesels

BMK34 Single Remote By-Pass System

BMK34 Single-Remote By-pass System
Cummins 5.0/5.9/6.7L Single-Remote Bypass System provides superior filtration performance for 2004 to current Cummins 5.0/5.9/6.7L engines while working in conjunction with the engine’s full-flow oil filter. This system connects to the engine through a full-flow filter adapter and oil fill port. System includes mount, mounting hardware, EaBP90, hose and hose fittings. Note: Full-flow filter not included with this system. Nissan’s 5.0L Cummins requires the optional BK1104

BMK34 Installation & Servicing Instructions

Currently there is no Dual By-Pass System recommendation for these engines. (4/1/19) If you have a question, check with us and we will contact AMSOIL Tech Support for more information.


Ford 7.3L Diesel

AMSOIL BMK21 Universal Single Remote By-Pass System

BMK21 Universal Single Remote By-Pass System
Universal Single-Remote Bypass System provides superior filtration performance while working in conjunction with the engine’s full-flow oil filter. This system connects to the engine through a pressurized oil port . System includes mount, mounting hardware, hose and hose fittings. Note: The EaBP bypass oil filter is sold separately. EaBP120 will not work with this system.

BMK21 Installation & Servicing Instructions.


BMK26 Dual Remote By-Pass System

BMK26 Dual Remote By-pass System For Ford 7.3 Diesels
The BMK26 Dual Remote Bypass System provides superior filtration performance for 7.3L Ford PowerStroke diesel engines. System includes mount, mounting hardware, hose, hose fittings, spin-on adapter, EaO26 full-flow oil filter and EaBP100 Bypass filter.

BMK26 Installation & Servicing Instructions.

Ford 6.0L / 6.4L Diesels

BMK31 Single By-Pass Filter

BMK31 Single-Remote By-pass System
Ford 6.0/6.4L Single-Remote Bypass System provides superior filtration performance for Ford 6.0/6.4L engines while working in conjunction with the engine’s full-flow oil filter. This system connects to the engine through the filter housing and oil fill port. System includes mount, mounting hardware, EaBP90, hose and hose fittings. Note: Full-flow filter not included with this system.

BMK31 Installation & Servicing Instructions.

Due to cartridge type full flow filter, there is currently no Dual Remote By-Pass System available for the Ford 6.0L / 6.4L Diesels.

Ford 6.7L Diesel

BMK33 Single Remote By-Pass System

BMK33 Single-Remote By-pass System
The Ford 6.7L Single-Remote Bypass System (BMK33) is designed for 2011-present Ford* Super Duty* 6.7L Diesel Pickups. It includes all components necessary for installation (including parts, hose, Ea Bypass Oil Filter and installation instructions), providing increased convenience and value.

BMK33 Installation & Servicing Instructions.


BMK28 By-Pass System

BMK28 Ford 6.7L Dual Remote By-pass System
The Dual Remote Bypass System provides superior filtration performance for 6.7L Ford PowerStroke diesel engines. System includes mount, mounting hardware, hose, hose fittings, spin-on adapter, EaO26 full-flow oil filter and EaBP100 Bypass filter.

BMK28 Installation & Servicing Instructions.

GM 6.6L Diesel

BMK32 Single Remote By-Pass System

BMK32 Single-Remote By-pass System
GM 6.6LSingle-Remote Bypass System provides superior filtration performance for GM 6.6L engines while working in conjunction with the engine’s full-flow oil filter. This system connects to the engine through a full-flow filter adapter and oil fill port. System includes mount, mounting hardware, EaBP90, hose and hose fittings. Note: Full-flow filter not included with this system.
BMK32 Installation & Servicing Instructions.

BMK27 Dual Remote By-Pass System

BMK27 Dual Remote By-pass System
The Dual Remote Bypass System provides superior filtration performance for 6.6L GM Duramax diesel engines. System includes mount, mounting hardware, hose, hose fittings, spin-on adapter, EaO26 full-flow oil filter and EaBP100 Bypass filter. Note: This Bypass system can also be used on 1990’s GM light-duty pickups equipped with the GM 6.5L diesel engine.

BMK27 Installation & Servicing Instructions

For Heavy Duty On And Off Road Applications

BMK30 Heavy Duty By-Pass System

BMK30 Heavy-Duty By-pass System
The AMSOIL Heavy-Duty Bypass System (BMK30) provides superior filtration performance for heavy-duty on- and off-road applications. It is designed specifically for the Ea Heavy-Duty Bypass Filter (EaBP120), bringing Ea synthetic technology to the heavy-duty market. System includes mount, mounting hardware, hose, hose fittings and the EaBP120 Bypass filter.

BMK30 Installation & Servicing Instructions

BMK22 Dual-Gard By-Pass System

BMK22 DUAL-GARD By-pass System
The Dual Remote Bypass System provides superior filtration performance and is ideal for engines with sump capacities greater than 20 quarts. The DUAL-GARD system links two AMSOIL Bypass filters together on one mount. This system connects to the engine through a pressurized oil port. System includes mount, mounting hardware, hose and hose fittings. Note: The EaBP bypass oil filters are sold separately. The EaBP120 will not work with this system.

BMK22 Installation & Servicing Instructions

By-Pass Filter Sizes and Capacities

1 While all of the oil flows through a full flow filter, in some circumstances it doesn’t all go through the filter medium. For example: when oil is very cold it may be too thick to flow through the filter material. If the oil is very dirty and plugs the filter material it will also reduce the flow. When this happens, a by-pass valve (not to be confused with a By-Pass Filter) opens and allows unfiltered oil to flow to the engine. If the oil is cold, it will warm as the engine warms and will thin enough to allow sufficient flow through the filter material at which point the by-pass valve will close. If the by-pass valve opens due to a dirty / plugged filter, the only option is to replace the filter.

*All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use. All products advertised here are developed by AMSOIL for the use in the applications shown.

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.