Here are a few points that must be considered before purchasing a bypass filter for your diesel engine.


Webster’s New World Dictionary defines filter this way: “a device for separating solid particles, impurities, etc. from a liquid or gas by passing it through a porous substance.” With that in mind, the primary purpose of any bypass filter is to remove particles and impurities from the oil to extend the service life of the oil and to stop the wear in the engine. Since the gaps between the moving parts in your engine are between 2 and 22 microns in size (depending on the crank position), when you are shopping for a bypass filter only consider those filters which can PROVE (“prove” means 3rd party independent lab test results with particle counts upstream of the filter being tested and downstream of the filter with beta ratios published) that the filter is as close to 100% efficient in the 2 to 22 micron range as possible (3 microns is 0.00012 of an inch). By removing all the particles in this size range, you will stop over 90% of the wear in your engine. Since these size particles will bridge the gaps between the moving parts in your engine removing them will break the “chain reaction of wear”. To illustrate, if you could walk an inch off the ground the soles of your shoes would never wear out. The same is true for your engine. If there is nothing between the moving parts but clean oil, there can be no (or very, very, very little) wear possible. When cleaning to this level you will also control contamination that is produced in the engine (primarily soot) or ingested from the outside. This will allow you to get the maximum life from your oil and your engine saving you thousands of dollars per truck per year.  The FS-2500 is 99.9% efficient on all particles from 3 to 50 microns in size.

  1. FLOW RATE –

Before you purchase a bypass filter for your truck you should know about the filter’s flow rate; or how much oil flows through the filter in one minute. This is a very important statistic to know since your engine is producing and ingesting contamination every second that it is running. If the flow rate of the filter is not up to the task it will make little or no difference that the filter is on your engine. Let’s say the bypass filter you are considering flows at a rate of 3 quarts per minute – at that rate it will take about 15 minutes for 11 gallons of oil to move across the bypass filter element. If the filter flows 2 quarts per minute it will take 30 minutes for 11 gallons of oil to move across the bypass filter element. So in these two examples all the oil in your engine will pass across the bypass filter element 4 times an hour if the filter flows 3 quarts per minute and just 2 times every hour for a filter that flows 2 quarts per minute. Depending on the amount of work that is asked of your engine and the amount of fuel that it burns these flows rate may not be enough. Even if the bypass filter was 100% efficient at 3 microns; at these flow rates the bypass filter is allowing engine wearing particles ample opportunity to engage the moving parts in the engine and cause wear long before they are removed. Couple that with efficiencies that can be less than 20% and you have situations in which damaging particles can increase unabated and the bypass filter is out gunned and it can never keep up with the contaminant accumulation. Instead of contamination control (the reason you want a bypass filter in the first place), you have contamination out of control! To illustrate this better, let’s say you are in a boat which is taking on water and will soon sink. If the boat is taking on 200 gallons of water per minute and the bilge pump working at 100% capacity can handle 250 gallons per minute, you might be alright. But, if the bilge pump is only capable of pumping 50 gallons per minute max, the incoming water (contaminants) will be too much for the pump to handle and for all the good it did (in this scenario) its presence was irrelevant. So, when shopping for a bypass filter the #1 spec to look for is efficiency followed closely by flow rate.  The FS-2500 meters the flow of oil within the matrix of the element itself. The average flow rate throughout the life of the element (10,000 miles for Class 8 trucks) is 1.5 gallons per minute. This is very slow relative to what your oil pump is displacing, but fast enough to keep up with contaminant creation/ingestion. All the oil in your engine will move across the element in the FS-2500 8 TIMES PER HOUR. That flow rate, coupled with 99% efficiency on all particles 3 microns and bigger, makes the FS-2500 a very effective tool for controlling all contamination that will fit between the moving parts in your engine and cause wear very quickly after they appear on the scene.


When considering the purchase of a bypass filter, the price you pay up front is not the only cost you have to consider. You also need to factor in how much the bypass filter will cost you to use per year. A lot of bypass filters on the market today hold 1 to 5 gallons of oil in them. When you change the bypass filter element(s), typically every 10,000 miles or so, you need to consider the cost of that displaced oil. If all bypass filters performed equally (which they do not!) the cost of oil needed to fill up the filter could limit your choices considerably. Here is a quick table to refer to once you figure out how much oil the bypass filter that you are thinking about displaces:


3 quarts 9.75 X $14.00 $136.50
1 Gallon 13 X $14.00 $182.00
2 Gallons 26 X $14.00 $364.00
2.5 Gallons 32.5 X $14.00 $455.00
3 Gallons 39 X $14.00 $546.00
4 Gallons 52 X $14.00 $728.00
THE FS-2500
1.5 Quarts 4.875 X $14.00 $68.25

The FS-2500 only displaces 1.5 quarts of oil and in this example would only require you to buy 4.875 gallons of oil per year to service the filter. That would be less than $350.00 in five years. If a bypass filter held 2.5 or 3 gallons of oil – that would be $2,275.00 and $2,730 respectively in five years. The FS-2500 is greener than the others in more ways than one!


Bypass filters under your consideration should be easy to install by a non-professional in a relatively short period of time (1 to 2 hours max) with common tools. The bypass filter should automatically come with a complete custom installation kit – not an option with an up-charge! Then you can do it yourself without hiring a shop to do it for you (more money gone, more time gone and since time is money; still more money gone!!). No going shopping to buy the supplies and fittings needed for installation. No reinventing the wheel figuring out how to install the thing.  The FS-2500 is sold with an engine/ chassis specific kit custom for your truck and engine combination. The kit comes with 3/8” stainless steel hose cut and crimped to length and also comes with all the hardware and adaptors needed to connect the filter to your truck and to your engine. So you don’t have to reinvent the wheel, the kit comes with step by step instructions with digital pictures so you can’t go wrong in the 1 to 2 hours that you spend installing the FS-2500.


Any bypass filter that is under consideration should be compact in size so servicing the filter is not problematic when you’re away from home. It should allow several options for mounting. Any bypass filter at the top of your list should be able to be mounted in ANY position, at ANY elevation relative to the engine and preferably in the engine compartment or under the hood so that the filter is unseen and the hoses connecting the filter to your engine are relatively short (they are rather like jugular veins and should not be super long or exposed to potential damage). The FS-2500, in almost every Class 8 application, mounts to the outside of the frame rail of your truck under the hood on the passenger side (from time to time on the driver’s side). The hoses are typically less than 35” long and the Class 8 kit comes standard with stainless steel braided hose with a TEFLON inner tube. This makes them virtually bullet proof against heat, after all, this is the same hose used on most turbo chargers. The FS-2500 can be mounted horizontally or vertically. The FS-2500 does not need electrical hookups, air supply, nor does it have any moving parts. The FS-2500 does not have to have complicated and worrisome flow adjustments or multiple units to deal with.


When looking at which bypass filter to purchase, consider closely claims about a filter’s dirt holding capacity. While on some level this might be considered valuable information, it may not be as important as it seems at first glance. First of all, how can a company tell you, in a way that you can trust, that a filter held “x” amount of contaminants? They can say “we ran a test and we added so much stuff to the filter every hour for so many hours and all those additions add up to “x” ounces or pounds of contamination”. That is not a good enough explanation. To illustrate the point, let’s say you have a 55 gallon drum with 30 gallons of oil in it and you have a pump hooked up to the drum to circulate oil. You start your test by adding 5 ounces of dirt per hour to this drum and you do that for 2 full days, which means that you added 240 ounces (or 15 pounds) of dirt to this drum in 48 hours and if someone was given these facts, they would have been told the absolute truth. Now, we install a filter between the pump and the drum and do the same test, we add 5 ounces of dirt per hour for 48 hours and the filter never clogs and the pump doesn’t shut down because it has adequate flow for the entire test. Can you honestly say that the “filter” held 240 ounces or 15 pounds of dirt? Not necessarily, we already know that the 55 gallon drum will hold 15 pounds of dirt added to it at a rate of 5 ounces per hour for 48 hours. But now that we have introduced a filter to the mix we need to know how many of those ounces actually went in to the filter. If the filter in this example had 1% efficiency and could not catch any size particle, all of the dirt introduced every hour for 48 hours would pass right through the filter. You could “honestly” say that 240 ounces or 15 pounds of dirt were added to the “test bench” (the 55 gallon drum, the filter, the 30 gallons of oil and the pump) but how much got into the filter? The only way you can know how much of the 15 pounds of dirt in this example ended up in the filter is by counting the particles (or ounces) that were added upstream of the filter and then counting the ounces downstream of the filter. Then, and only then, can you “honestly” know how much of the 15 pounds of dirt ended up in the filter. If that crucial information is missing, the test is invalid and the “claim” of holding 15 pounds of dirt is suspect at best! There is a much more important stat to know and it combines three factors. As mentioned from the outset, efficiency is at the core of “filtering” so once again the most important thing is the efficiency of the filter, followed closely by the flow rate of the filter and finally the service life of the element. If the filter is as close as possible to 100% efficient at removing the particles that damage your engine and contaminate your oil (which forces you to change it prematurely) AND it flows at a rate sufficient to keep up with contaminant production AND it will survive for an economical amount of time, how much it holds is irrelevant. Let’s face it, if you have a bypass filter that is 100% efficient at 3 microns and you have to change it every 3,000 miles, that’s not helping you at all. But if you have a filter that is 100% efficient and it last 10,000 miles that’s more like it. Does it matter to you that the filter stopped 100% of the particles that cause wear in your engine? Of course it does. Does it matter to you that the filter stopped the contamination fast enough and efficiently enough to get you an oil drain interval many times longer than you had before the filter was installed? Of course it does. At the end of the day, what does it matter if your filter held 8 pounds or 15 pounds or 100 pounds? If the filter is PROVEN to remove as close to 100% as possible the particles in your oil that cause wear AND flows at a rate high enough to keep up with contamination production AND will survive for 10,000 miles or more…that filter holds all that it needs to hold irrespective of what that number actually is! The FS-2500 is no less than 99% efficient on all particles 3 microns in size or larger. The FS-2500’s flow rate is 1.5 gallons per minute. The element in the FS-2500 needs to be changed once every 10,000 miles. You do not change the OEM filters on the engine until you change your oil or at least once a year whichever comes first.

In Summary:

There are quite a few things to think about when considering a bypass filter for your truck. After all, it’s your livelihood we’re talking about here and these days every minute and every penny count. We have touched on just six points, but these are very important when you are considering spending your hard earned money on a bypass filter. In fact, these six points are so important that any bypass filter that can’t easily and clearly address them just might not be good enough to make your final cut. But it’s your truck, so that will be your call to make.

If you have any questions or need more information about bypass filters in general or the FS-2500 specifically, please don’t hesitate to give us a call. We would be glad to answer any questions you have!

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