How Fuel Filter Micron Size Matters in Diesel CFPP

How Filter Micron Size Matters in Diesel CFPP (Cold Filter Plug Point)

When winter is upon us, we always wish we were more prepared. This research article is written to help you understand the vital role of diesel fuel filters and specifically their rated micron size and how this affects extreme cold weather performance. This is informational and as our disclaimer states below… always consult with the engine manufacturer and use a quality lab for fuel and fuel filter testing. Fuel & Friction does not warranty or guarantee the third party provided information contained herein and is for informational purposes only.

With all the preparation and precautions that are taken for your diesel powered truck or construction equipment… quite often, a weather system will bring in a cold front and severely cold freezing temperatures. During these times you may experience a diesel engine non-start condition or freeze up of a diesel engine. We’re not talking about the anti-freeze either, this has to do with fuel and fuel filters for the purposes of this article.

Water Contamination

Is the most common form of contaminant. It may be introduced into the fuel supply during warm periods when moisture forms in the tanks and condenses on the cold metal walls of the fuel storage tanks or from poor housekeeping practices. Water can seriously damage the injector components and can contribute in the reduction of lubricity of the fuel which can harm components that work with close tolerance – for example the fuel pump assemblies.

Water Contamination Remedy

Water can be removed from the diesel fuel by using in-line water separating filters or devices. Your best and easiest method of prevention is to purchase fuel from reputable suppliers that can provide high quality fuel on a consistent basis. Also keeping the tank as full as possible at all times prevents condensation. Bottom line: Be sure to change your fuel filters more often in the winter months. Water is a filters worst nightmare.

Wax Contamination

Wax is a source of energy in fuel but needs to be controlled in cold weather operations. Diesel fuel contains paraffin which provides the engine with proper lubrication. However, cold temperatures that can make fuel go below it’s cloud point, which results in wax precipitation and filter plugging .

Wax Contamination Remedy

To prevent wax formation the cloud point of fuel must be at least +12° Celsius (+22°F) below the lowest outside temperature. Fuel suppliers blend diesel fuel based on local anticipated cold weather conditions, but this method is slowly becoming obsolete. Using a Fuel Conditioner such as CleanBoost® Sno-Cat™ helps shield your fuel from wax crystals forming. It’s easy to use, fast to dose and inexpensive to run. This makes it one of the best and most efficient winter diesel fuel dosing choices around.

We reached out to Combustion Technologies for additional insight on filter micron sizes and the effects since 2007.

Disclaimer: The following information is provided for reference only on an as-is basis, with no warranty express or implied as to the correctness or viability for your particular situation or application. Be sure to test your fuels with a quality lab for analysis and check with your equipment or vehicle manufacturer before applying or installing any non-factory approved filters. Fuel & Friction does not recommend or accept any liability as to how you may use this information.

We have news for you. Diesel fuel filters are not all created equal. They all have different filtering medias and micron ratings for a reason. This reason has to do with their specific application for which they were originally designed for. Since 2007, ULSD (Ultra Low Sulfur Diesel) fuels have become the standard for us here in the United States and other regions.

The Challenge

ULSD fuel does bring with it, new challenges when it comes to lubricity and overall quality. Testing fuels is something that you should consider for your fleet if you’re at all serious about reducing maintenance costs and keeping trucks and equipment running at peak efficiency. Testing and performance at ultra cold temperatures is another story entirely.

With the help of SGS / Herguth Labs, testing was performed comparing filter medias and micron ratings to see the difference between 3 types of filters:

-Baldwin Fuel Filter – 30 micron rating
-Wix/Napa Fuel Filter – 15 micron rating
-Cat/Donaldson Fuel Filter – 2 micron rating

The results are intriguing. The Pour Point was never affected, however the Cold Filter Plugging Point displayed a big drop in temperature performance depending on micron rating of the filter. Click on image below to view its entirety:

Pour Point Test

Pour Point Test with Different Filter brands and Micron Sizes

Cold Filter Plug Point (CFPP) ASTM D6371 – This test is a more complicated procedure which involves using a vacuum to draw a 20cc fuel sample through a 45 to 50-micron screen within a 60 second time period. Up until 2007, the introduction of ULSD (Ultra Low Sulfur Diesel), many if not most operators used CFPP to provide a reference temperature for cold weather operability with diesel fuels. This is however a complicated and imperfect test. As mentioned above, CFPP uses a vacuum to draw a sample of the fuel through a 45 to 50- micron screen within a given time.  The point at which the sample fails to go through the screen in 60 seconds is the CFPP. The main issue is that up until 2007, most fuel filters used by operators were a 30-micron rated media. Todays OEM Engine Manufactures recommend using a 2 to 10-micron filter to help protect direct injection applications as well as keep the fuel system cleaner due to ULSD quality fuels. The significant difference of 10 microns and 45 microns caused a disparity between the test and real world operations. However, many in the industry felt that this differential was consistent and provided a reliable guide for cold weather operability. For example, if testing showed you had a CFPP of -24°F, you could feel reasonably confident that you could operate to -10°F using a 10 micron fuel filter for the engine.” – (source Brett Winberg – Combustion Technologies USA.)

In other words, due to ULSD quality fuels, most engine manufacturers today recommend using a 2 to 10 micron filter. The test showed that CleanBoost® Sno-Cat™  has a tremendous effect on Pour Point, Cloud Point and Cold Filter Plugging Point performance at the different filter micron ratings. All testing above was done at a mix ratio of 1:2,000 which took a Pour Point performance from -8° Fahrenheit to -44° Fahrenheit. The Cloud Point performance from 10° Fahrenheit to -4° Fahrenheit… and finally, the Cold Filter Plug Point performance from -2° Fahrenheit to -29° Fahrenheit (Baldwin filter), -20° Fahrenheit (Wix/Napa filter) and -14° Fahrenheit (Cat/Donaldson filter). Again, this is based on using CleanBoost® Sno-Cat™ at a mix ratio of 1:2,000, which equates to 16 oz of CleanBoost® Sno-Cat™ to 250 gallons of ULSD diesel fuel.

When it comes to severe cold weather snaps in your area, you may want to consider this information vital to your truck or equipment fleet to keep it starting and running in these extreme temperatures.

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Tech Guy

Automotive enthusiast, passionate about Jeeps, hot-rods, turbos, performance, efficiency, diesels, fuels, high performance oils, additives and anything with an engine.

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