Introduction
If you’re exploring alternative fuels like black diesel, waste motor oil (WMO), waste vegetable oil (WVO), or biodiesel, you know that cleaning waste oil is a major step before using it in a diesel engine. The two most common ways to filter waste oil are using a waste oil centrifuge or filters. But which one works best? A research study on waste motor oil as fuel has some surprising findings about how well each method works—and why filters might not be as good as you think.
The Problem with Dirty Waste Oil Filters
When oil is used in an engine, it picks up metal shavings, dirt, soot, and water. If you burn it in a diesel engine without proper cleaning, these contaminants can cause serious damage.
“The particles entrained in the high-pressure fuel essentially act as a sandblasting media as it passes through the pumps and injectors,” the study explains. “The most damaging particle sizes are in the 2-10 micron range. They are also the most difficult to filter out.”
To prevent engine damage, WMO needs to be filtered down to at least 1 micron, which is the standard size for diesel fuel filters in many modern engines, like the Cummins QSK38. But how do you remove these tiny particles?
How Cartridge Filters Work (And Their Hidden Problems)
Many people use cartridge filters (like the ones in diesel trucks) or sock filters to clean their waste oil. These filters are rated at different micron levels, such as 10 microns, 5 microns, and 2 microns. The idea is that oil is pushed through the filter, trapping dirt and metal inside. But there’s a big problem—filters can actually add contamination back into the oil!
The study found that some filters released more debris than they removed. “In every single metal species, the cartridge filter sample actually added more contaminants to the sample or remained the same instead of removing anything,” the research states. This happened because the filters were already partially clogged from previous use, causing them to release trapped particles back into the oil. Oil filters have to be changed frequently or you risk contaminating batches with more debris than you started with.
Filters also have another issue: they can’t remove water from waste oil. If you burn WMO with water in it, you risk damaging your injectors and creating steam in your fuel system.
How Centrifuges Work
A waste oil centrifuge operates using centrifugal force to separate contaminants from the oil. Instead of pushing oil through a mesh or paper filter, the centrifuge spins the oil at high speeds. Heavier contaminants like metal shavings, dirt, and sludge are forced to the outer edge, while the cleaner oil remains in the center and is drained off. This method ensures that even the smallest impurities, which often slip through cartridge filters, are removed effectively. The two styles of centrifuges are bowl style and pressure driven, which is explained below.
“A bowl-type centrifuge is a bowl that spins at … (high) [r]pm. The centripetal force due to centrifugal motion causes the WMO to be pushed up against the walls of the bowl. Heavier particles will stay against the wall while the good oil rises to the top towards the hole in the middle then will drop out into a container below.”
“A spinner-type centrifuge is powered by the force of the pumped oil itself. Pressurized oil is pumped through the rotor and the velocity of exiting oil through jet nozzles powers the centrifuge.”
Centrifuges are capable of filtering waste oil down to sub-micron levels. The study found that centrifuges consistently removed contaminants without reintroducing them into the oil, unlike cartridge filters. This makes them highly efficient at purifying waste oil for alternative fuel use.
Why Centrifuges Clean Waste Oil Better
One major advantage of using a centrifuge is that it does not clog like traditional filters. Cartridge filters lose efficiency as they accumulate debris, requiring frequent replacements and maintenance. A centrifuge, on the other hand, can process large volumes of oil without losing effectiveness.
“The process may need to be stopped periodically to disassemble the bowl for cleaning. This involves scraping sludge from the bowl. This sludge will probably be surprising to the user as to how much contamination could have been missed by other methods previously mentioned.”
Another significant benefit is water removal. Water in fuel can cause injector damage, reduce combustion efficiency, and lead to engine failure. Cartridge filters are ineffective at removing water from oil, but centrifuges successfully extract moisture, ensuring a cleaner and more engine-friendly fuel.
“A spinner-type centrifuge is capable of filtering down to one tenth of a micron but is not intended to remove water or antifreeze. However, the centrifuge did have a slight effect on water removal, reducing contamination by up to 23% in one test.”
From a cost perspective, centrifuges are a long-term investment. Depending on fuel costs in your area, producing as little as 350 gallons of black diesel is a 100% ROI. While they may require a higher initial cost, they eliminate the need for constantly replacing filters. The research study found that cartridge filters not only became saturated quickly but sometimes worsened contamination. “There were eight species showing negative removal rates, meaning that material was added into the oil by the filtering process.” In contrast, centrifuges provide reliable purification without the cost of filter replacements.
Take Control of Your Fuel Production
If you’re serious about producing fuel for 10¢ a gallon, you need a solution that works. The Ultimate Force Centrifuge was built for fuel producers like you—designed to remove harmful contaminants, extend the life of your engine, and give you the cleanest fuel possible. Stop wasting time with ineffective filters. Get the Ultimate Force Centrifuge today and start producing high-quality fuel with confidence.
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Citation
Bierhaus, Zachary S., “Feasibility and Environmental Implications of Using Waste Motor Oil as Alternative Supplemental Fuel in Contingency Prime Power Generation” (2017). Theses and Dissertations. 807.