This is one of the great riddles for 4WD owners trying to keep their rigs ‘track ready’.
The question everyone seems to be asking me of late is – primary or secondary fuel filter?
A primary filter usually filters to 30 micron while a secondary filter works around the 2-5 micron mark.
Now unfortunately I don’t have the equipment to carry out proper testing but the next best thing is to chat to the boys that do.
Directions Plus is making a huge splash in the market and are a company that supplies catch cans and primary filter kits.
The question you have to ask yourself is… in this case do you want to filter fine dirt particles or are you looking to filter water from the system?
If you are looking to catch dirt particles then a secondary filter will be the go for you but you will also need to check on the efficiency of the filter.
Nominal Micron Rating
This refers to how capable the filter is when it comes to capturing particles of a \at an efficiency between 50% and 90%. For instance, a nominal rating of 50% at 10 micron simply means that filter captures 50% of the contaminants that are 10 micron in size.
Keep in mind that nominal micron ratings may range anywhere from 50 – 98.6% efficiency at removing the specified particle size.
Absolute Micron Rating
This term refers to a filter that’s capable of removing at least 98.7% of a specific sized particle.
This rating is determined through a test in which fluid passes through a flat sheet of filter material. Particles that pass through are measured and counted. This rating is more informative than the nominal micron rating.
If you are looking to filter water then it’s a bit more of a challenge. A filter’s ability to separate particles is different to its ability to separate water.
The main issue comes with the emulsified water particles that seem to get pushed through the filter.
Flow rate has a dramatic effect on the filters ability to catch and filter these particles. A coarse filter has a much better filtering capability to filter this kind of water then a finer filter.
On the other hand, a primary filter is better at blocking emulsified water. The problem is that as the water is mixed or attached to the diesel fuel it becomes a lot harder to trap.
In this instance, it’s best to fit up a primary filter and then let the factory filter do its job filtering anything that may get past the primary.
Most factory filters will filter down to anywhere between 7 to 2 microns so they will do a good job of stopping anything further. Primary fuel filters have been used for years on trucks and have done a great job.
The ultimate is to fit up a Directions Plus fuel filter and catch can kit. I’ve just bought myself a new project. 2013 Landcruiser 200 series and this is one of the first things that I’ll be fitting up.