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Why By-pass Filters?

Taking Your Fleet The Extra Mile
by  Don S. Culpepper, V. P. Engineering
(Note!  The following was written for inclusion in GCF's Brochure for state Department of Transportations.  Also, at the time, CG4 was the highest rating of oil for diesel engines.)


For several years now there has been an industry wide push for extended oil drains on fleet equipment. This industry demand for extended oil drain intervals is an effort to reduce downtime, reduce waste oil generation and the on-going search to cut maintenance cost. Extended oil drain intervals can offer huge benefits for DOT fleets, providing the extended oil drain program is structured to ensure engine life is not compromised.

Currently, the most preferred means to extend oil drain intervals has been an effort by the oil manufactures to develop new oils, with improved additives packages, to extend oil drain intervals. Within most any magazine to do with fleet maintenance you will find several advertisements boasting about their "NEW" oils. They all have claims of achieving extending oil drain intervals, some up to 40,000 miles. However, simply selecting a new type of oil and taking the "Pour in & Go " approach is not the single answer to extended oil drain intervals.

This article will explore a time proven program that has proven to drastically extend lube oil drain intervals. This program also has proven to extend the life of the equipment, reduce downtime, reduce maintenance man-hours, cut waste oil generation up to 70% and is highly cost effective with a payback of usually less than one year. This article will also cover the problems and hurdles encountered when exploring extended oil drain programs. There are problems such as soot control and other contaminants within the oil that must dealt with to achieve greatly extended oil drain intervals.

This program does not rely on new technology, rather it utilizes standard technology that has proven itself for over twenty (20) years. For the most part, this program utilizes Ultra Fine (UF) by-pass lube oil filters and a comprehensive monitoring program to track wear and oil condition to detect potential problems within the equipment during extended oil drain intervals. Some of the users of this program include: Offshore operations of Shell Oil & Chevron USA, Scott Paper Co., North Carolina DOT, US Air Force, US Army, US Navy, US Marine Corps and many other prominent Companies. The following paragraphs are a brief outline of the GCF program.

P/PM Program Outline

1. Standard Petroleum Lube Oils: Utilize Standard API CG rated petroleum based lube oils in lieu of more expensive or full synthetic oils. There is no need for synthetics to achieve extended oil drains, when using UF by-pass filters. However, other benefits, such as low pour points for cold weather applications, should be looked at by certain fleets.

2 Add UF By-Pass Lube Oil Filters to remove solid and moisture contaminations from the lube oil. These filters will keep the equipment running on clean oil 100% of the time, thereby reducing wear and eliminating the need for routine oil drains.

3. Utilize The GFC Portable Oil Quality Analyzer at all maintenance locations. This simple portable oil analyzer will allow maintenance personnel to analyze the quality and condition of the lube oils and equipment condition in their own shops. By doing so, they can began to detect potential problems before unnecessary downtime would occur.

4. Use Complete Laboratory Oil Analysis. If you are already utilizing complete oil analysis, continue to do so to monitor wear rates and compile information on your equipment for use in long term trend analysis. However, by using the GFC Model 126 Portable Oil Quality Analyzer, this portable analysis will enable you to extend the sample interval for complete laboratory oil analysis.


The majority of DOT fleets in the U.S. currently operate their equipment with standard factory filtration and manage them with a standard factory recommended P/M (Preventive Maintenance) Program. The standard filtration equipment referred to here generally refers to factory full flow filters only and in very few cases, factory full flow filters coupled with the use of marginal by-pass type filtration. The standard factory recommended P/M Program, that is normally followed by the maintenance industry is to follow the manufacture's recommended routine oil and filter drain intervals and in some cases utilizing complete laboratory used oil analysis as a P/M tool. This type of P/M Program is sufficient, providing that fleet managers will be satisfied with "Normal" equipment life expectancy and current expenditures. However, experience has shown us that most highly successful fleets do not become successful by doing what is "Normal."

A Lube Oil Maintenance Program, such as the GCF P/M Program, will take fleets far above and beyond a standard program. This type of P/M Program will move a fleet's Preventive Maintenance Program to one closer to a Predictive Maintenance Program. The utilization of UF by-pass filters within this program is a key factor. The by-pass filter performs the job of removing solid and moisture contamination to prevent additive depletion of the oil and dramatically reduces the amount of wear within the engine. Beyond the single goal of simply extending lube oil drains, this program reaches several other goals as well. The goals and benefits of this program are as follows: (1) Greatly extend and/or Eliminate oil drains. (2) Reduce wear within the equipment thereby extending the life of the equipment. (3) Reduce downtime to the equipment. (4) Reduce maintenance man-hours. (5) Reduce waste oil generation. (6) More cost effective than current lube maintenance programs and delivers a fast return on investment. The information on the following pages will fully explain the components of this program and how these components extend the oil drain intervals and achieve the goals listed above . These areas are as follows.

  1. Understanding lube oil and its job function.

  2. By-Pass filters, the key to wear reduction.

  3. Complete Laboratory and Long term equipment trending.

Selecting the Proper Filtration to Achieve Your Goal: 

The most integral portion of this program is the use of the By-Pass filter. There are many different types and brands of after market filters and centrifugal equipment on the market today that boast claims of greatly extending or eliminating routine oil drains. Many of these claims are true, however, in many cases the truth has been stretched by methods of marketing, claims based on “in-house testing” and testimony from isolated customer bases. Also, many of these filters and centrifuges fall short of dealing with and controlling the amounts and types of contamination that need to be removed in order to achieve our goal of extending and/or eliminating routine oil drains. In order to select the “Right” filter for the job, your choice should meet the following criteria and offer the following benefits: 

1. Choose filtration that has the ability to control 1- 5 micron sized particles and control them within the quantity that the engine or equipment is generating. Be sure to ask to see several particle counts taken on engines or equipment similar to yours showing ISO cleanness levels. These ISO levels show particle counts within the 5 – 50 micron range for engines oil and 2 – 50 micron range for hydraulic applications. Don’t be taken by what is said in the brochure, statements like “Capable of removing down to 1 micron particles” or “Can remove particles as small as 1/10th micron in size.” This type of marketing is common. In other words, for these companies to legally be able to advertise with such statements, all they have to do is to show that their filter or centrifuge has removed a few of this size particle. Sure these filters or centrifuges can remove “down to” and “as small as”, but can they control them in quantity? Get the particle counts! There are several depth-type by-pass filters on the market that have the capability of controlling these 1 – 5 micron sized particles. There are at least two brands of inexpensive centrifuges on the market that claim to be able to remove extremely small solids, however, I feel that they are overstated, ask for the particles counts. 

2. Choose filtration that has the ability to remove moisture from the lube and keep the lubricant chemically dry at all times. This is most critical. If you will remember, in order to control oxidation, nitration, acid formation, viscosity increases, and the other problems linked to moisture contamination, one must choose a filter that has the capability of removing moisture. Most all depth-type-by-pass filters with an absorbent filter media such as cellulose (paper) or cotton fibers have this capability. However, the low cost centrifuges that I mentioned above, do not have this capability. Only more expensive ($12,000.00 & up) centrifuges that are motor driven, equipped with water ejection ports and separator plates have this capability. These types are mainly used on extremely large engines such as found on ships. 

3. Choose filtration that has been proven within your field and that can be confirmed by several users and legitimate field test results. If at all possible, choose filtration that has been documented on your type of equipment and your type of operating conditions. Ask for field test results on equipment similar to your own, if the filter manufacturer can not produce this type of information, I would suggest that you look elsewhere. 

4. Choose filtration that is backed by a company that can offer a proven P/M Program to coexist with their product and our existing P/M Program. There are a lot of companies out there that specialize in selling filters, however, there are few filter companies that sell filters and specialize in Predictive preventative maintenance. Find the company that offers proven suggestions that will make their product work with your P/M Program and to help move your program up to a higher level of equipment monitoring and to help move your program up to a higher level of equipment monitoring. Also, select a company that has an unprecedented number of satisfied users and be sure to ask for a user list and call these users for their comments. 

5.  Choose filtration that is the most cost effective.  Last but not least and should be the most important, choose the filtration that is the most cost effective.  There are filter manufacturers that guarantee to double your oil change or to greatly extend your oil change interval.  Look for a filter that will offer to eliminate routine oil changes all together and run the maximum of hours between filter changes.  Gulf Coast Filters utilizes a massive element for holding huge amounts of contamination allowing you Longer filter change intervals.


The use of UF By-Pass filters and a comprehensive oil and equipment monitoring program has proven to greatly extend and/or eliminate routine oil drains. The benefits available to DOT fleets are significant, in that one can cut maintenance costs, extend the life of their equipment, reduce equipment downtime and reduce waste oil generation. 

There is an unprecedented number of satisfied users of UF By-Bypass filters and this type of P/M Program. 


SAE Papers: 912344, 810499, 852126, 881827, 881825 

April 1998 Issue: “Fleet Equipment” 

May 1998 Issue: “Lubes-n-Greases” 

Titan Laboratories 

Analysts Services Laboratories 

Shell Oil Test 1989 

Chevron Test 1991 


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Gulf Coast Filters
P.O. Box 2787
Gulfport, MS  39505