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A screw compressor oil filter cleans the oil that cools and seals the airend of an oil-flooded rotary screw compressor. Change it on the hours your compressor manual or controller gives, and sooner in dusty or hot rooms. When it clogs, a bypass valve lets dirty oil reach the screw element and bearings.
This guide is for workshop and plant managers who look after compressors that feed tyre shops, air tools and brake test benches. It covers what the filter does, the parts that are serviced with it, and how to order the right one.
What the screw compressor oil filter does
In an oil-flooded screw compressor, oil is injected into the airend. It cools the compressed air, seals the gap between the rotors and lubricates the bearings. The oil then leaves with the air, is separated in the oil tank, cooled and sent back to the airend.
The oil filter sits in that return path. It removes particles before the oil goes back to the rotors and bearings. Kaeser's maintenance checklist describes it simply: the lubricant filter removes particles from the oil circulating in the airend, and the separator removes oil from the air before it leaves the machine (Kaeser maintenance checklist).
Most spin-on compressor oil filters have a built-in bypass valve. A service guide for rotary screw compressors says the valve opens when the oil is cold and thick or when the filter is dirty (oil filter operation guide). The idea is that dirty oil is better than no oil. The cost is that unfiltered oil then reaches the screw element and bearings (source: Air Compressor Guide, "The air compressor inlet filter"). A filter that is left too long does not stop the machine. It simply stops protecting it.
Oil filter, separator and oil: three parts, one service
The oil filter is only one of three parts that keep the oil circuit clean. They are usually checked together.
| Part | What it does | What tells you it is due |
|---|---|---|
| Oil filter | Removes particles from the oil going back to the airend | Service hours, controller message or filter monitor |
| Air/oil separator cartridge | Removes oil mist from the compressed air before it leaves the tank | Service hours, rising pressure drop, oil in the air lines |
| Compressor oil (coolant) | Cools, seals and lubricates the airend | Oil type, operating hours, temperature and oil analysis |
Kaeser's SK series manual lists the oil filter, the oil separator cartridge and the cooling oil as separate tasks with their own intervals. It also says the separator's life depends on the air drawn in and on keeping to the oil, oil filter and air filter intervals (source: Kaeser SK series operating manual). A dirty oil filter or old oil shortens separator life.
Separator pressure drop is the usual warning sign. Many controllers show it, or the machine has a gauge. One troubleshooting guide gives about 0.2 to 0.3 bar for a new element and a typical maximum of about 1 bar (source: Air Compressor Guide, "Separator element worn or damaged"). Oil in the air lines is not always the separator's fault. A filter maker's troubleshooting note lists a blocked or damaged scavenge line and a wrong oil level among common causes (source: FAI Filtri, "Air/oil separators: apparent failures").
When to change the screw compressor oil filter
There is no single interval for every machine. The model manual and the controller decide.
- Kaeser's SK manual gives each task as "up to" a number of hours plus a calendar limit. It says these are recommendations and must be shortened in dusty rooms, at high temperature or with frequent use (Kaeser SK service manual).
- Kaeser's general checklist gives a starting point of 1,000 hours for the lubricant filter and tells owners to use the micron rating the maker specifies (source: Kaeser maintenance checklist 2024).
- On Kaeser machines with SIGMA CONTROL, the controller signals each task. After the work, reset the matching counter and record it in the service log (source: Kaeser SK 21 service manual).
- After storage of more than 12 months, the same manual says to change the oil filter, the oil separator cartridge and the cooling oil before restarting.
Compressor rooms in Indonesian workshops are often hot and dusty. Plan on the shorter end of the range and keep a written log, so you can see how fast filters actually load up.
How to match a Kaeser oil filter
FDA supplies the OEM 6.3463.0 compressor oil filter, a spin-on oil filter with a built-in bypass valve for Kaeser air compressors. Its parts page lists a height of 144 mm, an outer diameter of 93 mm, an M22 female thread, a bypass opening pressure of 3 bar and a weight of 0.85 kg. Public listings give the same size with an M22 x 1.5 thread (Oxfil 6.3463.0 listing).
Check the suffix before you order. One reseller lists 6.3463.0/A2 at 96 mm by 147 mm with a 16 bar bypass value, which does not match the plain 6.3463.0 listings (source: Platinum International listing). A filter that only matches the thread can still have the wrong bypass setting. Our spin-on oil filter matching guide explains why thread alone is not enough.
FDA's filters category also lists compressor separators, such as Kaeser 6.3524.1 oil separator, Ingersoll Rand 24121212 air/oil separator, Atlas Copco 2911016000 oil separator kit and Donaldson P783499 air oil separator. These are quoted by part number. You can also browse Atlas Copco parts or search all numbers on the parts page.
Use the right compressor oil
Change the oil type only with the maker's approval. FDA supplies Ingersoll Rand 38459582 Ultra Coolant 20L, a synthetic coolant for oil-flooded rotary screw compressors. Ingersoll Rand describes it as a polyglycol-based coolant with up to 8,000 hours of run time and a flash point of 271 °C (520 °F) (Ingersoll Rand Ultra Coolant page). Its product sheet says the 8,000 hours, or two years, apply under normal conditions (source: Ingersoll Rand Ultra Coolant product sheet).
Do not mix a polyglycol coolant with mineral oil or another synthetic. Drain and flush as your compressor maker instructs before switching.
For hydraulic machines, filters work in a similar way. See our excavator pilot filter guide. For truck and trailer parts in general, see trailer and truck spare parts.
What to send for a quotation
To quote a compressor oil filter or separator quickly, send us:
- The compressor make, model and serial number from the nameplate.
- The part number printed on the old filter or separator, including any suffix such as /A1 or /A2.
- A photo of the old part and its label.
- The oil now in the machine, if you also need coolant.
- Quantity and delivery location.
Send these through the quotation form and we will confirm the match before we supply.
Common questions
What happens if a screw compressor oil filter is not changed?
As it clogs, the built-in bypass valve opens and unfiltered oil goes to the screw element and bearings. The compressor keeps running, but the oil is no longer cleaned.
How often should I change the compressor oil filter?
Follow your compressor manual or controller. Kaeser gives intervals as recommendations and says to change filters more often in dusty, hot or heavy-use conditions.
Is the oil filter the same as the oil separator?
No. The oil filter cleans oil going back to the airend. The air/oil separator removes oil mist from the compressed air before it leaves the tank.
What do I need to quote a Kaeser oil filter?
Send the compressor model and serial number, the full part number with any suffix, a photo of the old filter, quantity and delivery location.
Need trailer & truck spare parts?
Send the part number, a photo or the machine details. Our sales team replies by email with a priced quotation.