Protect Your Diesel Engine Before It's Too Late

Protect Your Diesel Engine Before it's Too Late - GreenMAX filter - Parker RacorMany engine manufacturers encourage or require diesel fuel pre-filtration to be installed before the on-engine or final filters. Why more filters? Because pre-filtration can more than double the life of the filter system. More importantly, it can provide cheap insurance against contaminated diesel fuel. A bad load of fuel, contaminated with water, bacteria, rust and dirt will block off engine filters in minutes. At best the overload of particles and water will shut the engine down. At worst, it can ruin the fuel injectors. Either way, the result can be very costly.

Diesel fuel pre-filters are generally larger than their on-engine counterparts, stopping bulk and emulsified water as well as trapping other contaminants before they reach downstream filters. Pre-filters with clear inspection bowls can also be a window into your fuel system health, alerting you visually to the presence of water and gross contamination before any harm is done.

Seasonal effect on fuel

During the warm season, a pre-filter/water separator operates with minimal maintenance which consists of a daily bowl inspection to drain off collected water and an occasional filter replacement. Maintenance requirements can quickly change when the weather and fuel supply turns cold. Waxes naturally present in diesel fuel can suddenly crystallize into a gelatinous glob that quickly plugs fuel filters. Diesel suppliers add #1 diesel and additives every winter to avoid diesel waxing, and engine systems generally have no problems if they stay in the region for which the diesel fuel was formulated.

However, the “no problem” scenario doesn’t always play out. An early storm with a sudden dip in temperature or a relocation to a colder region can cause filters to plug with wax and shut engines down unless extra heat is applied to the fuel system. 

Heating options for diesel fuel systems 

Three options to add heat to the diesel fuel system are outlined below:

Electric heaters

Electric heaters are essential cold weather accessories used to pre-heat fuel in a filter housing for a few minutes before engine startup. But due to power limitations, electric heat can’t provide the fuel flow for full engine load operation in severe cold conditions. Waxing will occur and some fuel will continue to flow, but it will not be sufficient to run the engine under load. For continuous engine operation, much more heat must be diverted to the fuel.

Fuel/coolant heat exchangers 

Fuel/coolant heat exchangers transfer excess engine coolant heat to the diesel fuel. Because the engine needs to warm up first before coolant heat becomes effective, a significant delay can be expected before heat transfer performance peaks.

Hot return fuel blenders 

Hot return fuel blenders are the most efficient way to add heat to a diesel fuel system. Diesel engines are often designed to return a significant flow of unused fuel back to the tank. To prevent wax build up on the filter, returning fuel heated by the engine, is blended at the pre-filter with cold fuel coming from the tank. If the fuel in the tank is warm, a thermally controlled valve diverts the return fuel to the fuel tank. In conjunction with electric heating at startup, this method is the fastest way to get an engine started and running smoothly in cold weather.

The solution for pre-filtration and year-round operation is Parker Racor’s new GreenMax™. The GreenMax™ is a heavy-duty, cartridge-based fuel filter/water separator available with electric and return-fuel heat options for cold weather operation using diesel and biodiesel blends. An electric heater located in the water collection bowl helps with cold weather starting while the hot return fuel blender keeps your engine running. Providing heat for diesel fuel avoids fuel waxing, engine shut down, and helps increase engine economy and improve emissions in cold weather.

The GreenMAX™ is designed with exceptional water-removing efficiencies for both bulk and emulsified water, very low restriction of fuel flow and high dirt-holding capacity. The heart of the system is progressive, dual-stage coalescing and filtration delivered by the patented Aquabloc® filter element.

Clean is the new green. GreenMAX™ is engineered for fast return on investment, and the operative word is GREEN – delivering a low-cost filter change-out, low-cost per installation, and environmentally friendly filter disposal.


Investigate more Racor Products.


GreenMAX™ high-performance, all-weather filtration features:

  • Heavy-duty design & construction
  • Patented, progressive two-stage Aquabloc® filter media
  • Large, high dirt holding capacity, bottom loading cartridge filter element
  • 2, 10, 30 micron and coalescing filter media available
  • Available hot engine return fuel recirculating heater
  • Available 12 or 24 volt bowl pre-heater
  • Available hand primer or fill port
  • Tough clear bowl with “quick turn” self–venting water drain
  • Flow rate up to 150 gph (560 lph)
  • Dual inlet/outlet ports for flexible connections
  • Compatible with biodiesel blends
  • Common mounting bolt hole pattern
  • Available water-in-fuel probe/sensor system
  • Meets and exceeds all OEM engine requirements and specifications


This blog was contributed by the Engine Mobile Filtration Team, Parker Racor Division


Related content:

Why Filter Diesel Fuel?

Water - A Diesel Engine's Worst Enemy


Have a question about Parker products or services? We can help: Contact Us!

Comments for Protect Your Diesel Engine Before It's Too Late

Eliza Cranston
I wasn't aware that the seasons had a big effect on fuel in your diesel engine. I just got a diesel truck for my business and I want to be sure I'm maintaining it so that I don't have to do too many repairs. I'll look into these options for heating my fuel. Which do you think is the most cost effective?
Steve Hardison
Eliza, The best solution depends on the truck. If you have the room, the GreenMax not only protects your engine from contamination, but is the best option for cold weather operation. (It requires return fuel heat from the engine—like a Cummins.) The cartridge filter decreases service costs over time.

The Racor 390RC pre-filter is an efficient, compact coolant heater system. It provides the same extra engine protection in a spin-on; but is slow to heat up and requires runs of coolant hoses.

The Racor 690R1230 series have an electric bowl heater. Again, this provides pre-filtration advantages but only works for starting in cold weather. Electric heat won't keep you running if the weather is severe.

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