“I’m fine! I’ve got 11,000 filters on my engine and nothing will ever, ever get through!”
We may not have had anyone say exactly that, but we certainly have had some interesting conversations about filters and how they protect an engine. This particular conversation is going to be really general. We can get into the nitty gritty in the comments or in another article if you all are interested…
First off: Micron Ratings. The bigger the number, the bigger the stuff that will get through the filter media. Typically speaking, the older diesel engines (or the less sophisticated fueling systems) will have larger micron filtration than the new and newer high pressure common rail systems of the last 15-ish years. This has everything in the world to do with the technological advancements in fuel injectors and how they put fuel in the combustion chamber of an engine.
As an example, a 1987 diesel would usually have a 30 micron primary filter and probably a 10 micron secondary filter on it. The standing joke is that you can “start it on diesel, run it on coffee, and shut it off on diesel. It’ll start again tomorrow.” Compare that to a 2024 Tier IV final diesel engine with a 7 micron primary filter and a 3 micron secondary filter and you can see the importance of a fuel maintenance program. The ’24 engine will undoubtedly have lower emissions and better fuel efficiency, but it will be much more finicky about fuel quality.
Secondly: Nominal – vs – Absolute filter ratings. A nominal filter will pick up 51% or more of its listed micron rating. Absolute filters pick up 98.8% or more of whatever they’re rated at (Go ahead, please fact check that if it seems odd to you!) There’s a “thing” in the filtration world called a Beta Rating (another Fuel For Thought topic for another day) that talks about capture capability on larger particle size as we work up the scale. That game is this: A 5 micron nominal filter might be a really good 20 micron filter and an Absolute 30 micron filter. Does it get sold as a 5 micron filter (which sounds really really good!) or is it an Absolute 30 micron filter (which is what it really is, but doesn’t sell as well)?
Finally: Particulate or Water Blocking? Particulate filters block solids from passing through them but can’t tell the difference between fluids. Is it diesel? Is it water? It doesn’t know, and it doesn’t care. It’s just here to stop the chunky bits…
Water blockers come in a couple of different forms. They absorb the water (like a paper towel) or they are treated with a chemical that “grabs” (or repels) water. They also block particulate matter along the way. Overall, a much better filter to have protecting the engine, but also more expensive.
Overall, our recommendation is to stick with what the manufacturer of your engines recommend. They designed the engine and the fuel system to run at certain pressures and built-in certain tolerances. Unless you’ve messed with it and need it to behave differently, stick with them! If you aren’t sure, feel free to ask! If we don’t know, we know the folks that will!
Happy New Year!
What’s in your tank? Do you know? Do you want to?
You should!
Fuel For Thought is designed to be more than a “Freshman class” in fuel quality control. We’re going to present some technical stuff in small bites. We hope you will find it both useful and entertaining.
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