Tiny particles of dirt and contamination in your fuel system can damage injectors, carburetors, and electric fuel pumps. Choosing the correct fuel filter (or filters) is critical to protecting sensitive fuel system components and maintaining adequate fuel flow and fuel type compatibility.

Understanding Microns in the Context of Fuel Filters

Fuel filters are designed to capture particles too small for the naked eye to see. The effectiveness of a filter is measured in microns, which is the size of the particles that it can reliably remove. Micron ratings range from two to 100, with smaller numbers indicating better filtration. However, choosing a filter with the smallest micron rating is not always the optimal choice, depending on its location and the type of fuel system you have.

The wrong filter in the wrong position can cause a pump to work harder, leading to premature pump failure or filter clogging. It’s best to follow the pump manufacturer’s filter recommendation, consider your specific situation, and use a fuel pressure gauge to monitor the system for pressure drop.

summit racing LS fuel filter and regulator
(Image/Summit Racing)

Comparing Filtration Range (in Microns)

  • 100 Microns – 100 micron filters are usually used as pre-filters to protect fuel pumps and keep larger debris from clogging your post-pump filter. They can be mounted in-line before the pump or in the tank. Pre-filters in the tank are often called sock filters or fuel strainers.
  • 40 Microns – 40 micron filters are generally used for carbureted engines after the fuel pump. Utilizing a 100 micron pre-filter with a mechanical fuel pump is still advisable.
  • 10 Microns – 10 micron filters are typically used after the fuel pump on fuel injected engines and must be paired with a 100 micron pre-filter.

Comparing Fuel Filter Element Material

When choosing your filter’s element material, consider fuel compatibility, reusability, and its location within your fuel system.

  • Paper Fuel Filters – Paper filters are often referred to as cellulose filters and are usually disposable. They should not be used with methanol or fuels containing more than 20 percent ethanol.
  • Stainless Steel Filters – Stainless steel filters are compatible with all fuels and can typically be cleaned and reused.
  • Other Filter Material Designs – Sintered bronze, microglass, and fiberglass filters are for post-pump use only and are generally non-cleanable.
dual outlet fuel filter installed on an amc 258 engine right ahead of carburetor
Sometimes your fuel filter’s orientation can be a big deal too—read this to learn why. (Image/OnAllCylinders)
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Author: Dave Matthews

Dave Matthews was a mechanic for the U.S. Army, a Ford dealership, and served for many years as a fleet mechanic for construction companies. Now a technical content producer at Summit Racing, Dave has spent decades working on everything from military vehicles to high performance race machines.