Why is there Oil in my Screw Compressor Air Tank?

Is oil okay in my tank?

Donโ€™t be alarmed if you find oil in your air compressor tank. Actually, all rotary screw compressors pass trace amounts of oil in the compressed air. The question is how much is the normal amount of oil in my compressor tank? 

Normal oil carry-over

Coalescing filters play a big role in keeping the oil out of your tank. Depending on the upkeep, maintenance and overall condition of the compressor will depend on how much oil is being passed along downstream. A trace amount of oil may appear in your tank, which is a normal amount typically seen and nothing to be alarmed about.

Excessive oil in your tank

If you have oil actually โ€œpoolingโ€ in your tank, you may have a few things going on with your compressor. Your separator may be saturated, punctured or even collapsed which is creating excessive oil carry over. Additionally, if the scavenger lines or check valves are plugged and not working, that will create excessive oil carryover.

Routine Checks to Help:

- Record the differential across your separator.
- Stay up on routine separator maintenance.
- Use Original OEM separator which is designed to remove the most oil carry over.
- Regularly drain your air receiver tank.

Do you have an idea for our #expertcorner?ย Let us know!

Useful links:

Book Your Compressor Service



Who we are and how Ash Air can help your business!

Ash Air has been around in New Zealand since 1979, and weโ€™ve grown into a nationwide company with international support and a reputation for quality and reliability.We look after all things compressed air for your business!

  • Reciprocating, Screw, air compressors
  • Vacuum pumps
  • Nitrogen
  • An extensive line of air treatment components

Ash Air's range of Chicago Pneumatic, Alup, Pneumatech, and Quincy compressors are used extensively around the world in industries ranging from oil and gas to food, automotive and farming, and we bring you these world class compressors here in the land of the long white cloud.Our technicians are compressed air equipment experts and are dedicated to addressing customer needs. Supported by a 13 locations nationwide, Ash Air offers one of the widest selections of compressed air equipment and parts available today in New Zealand.

Reliability and Efficiency

With Ash Air compressors, you can count on reliability and high performance for even the most demanding applications. We focus our efforts on the following:

  • Increasing uptime
  • Reducing unexpected repairs
  • Reducing energy consumption
  • Improving the cleanliness of compressed air


Talk to the team today:  CONTACT US CONTACT US

Read more from our #expertcorner


Just like any other equipment, a compressed air installation also requires the necessary maintenance work during its entire lifespan. Even though maintenance costs are only about 5 to 10% of a machine's annual operating costs, failure to budget for maintenance can have potentially disastrous consequences. …


The air dyer is one of the most ignored cooler in the system. A dirty condenser will cause water in the lines, or worse it will cause complete dryer failure. …


Using nitrogen is not about fully replacing CO2, but it can reduce their consumption of CO2 by close to 70%. Using nitrogen is about sustainability. Creating your own nitrogen is easy and will reduce the use of a greenhouse gas, which is better for the environment. It will also save you money as early as month one adding that savings to your bottom line. …


A question that is occasionally asked by our customers to Ash Air is 'what is the cost of compressed air?'ย  This article looks at the product costs involved with compressed air, as well as minimising the energy cost of compressors and cost allocation. When looking at these factors, we need to realise what causes dropped efficiency of your compressor, leading to increased costs of compressed air. …

Show More