Compressor oil change is the most frequent and most important service job on a screw compressor. In an oil-injected screw compressor the oil is not just a lubricant — it is the compressor’s “blood”: it cools, seals the gap between the rotors and protects the bearings. The wrong oil, or oil left in too long, is the most common cause of overheating, shutdowns and an expensive airend overhaul. This article explains what the oil does, how our oils differ — ROTAIR (standard, 2,000 hours), ROTAIR PLUS (4,000), ROTAIR Xtra (8,000), Food Grade and, for oil-free compressors, ROTAIR Gear — and how to choose the right oil and change interval.
1. What the oil does in a screw compressor
- It cools. The oil absorbs most of the heat of compression and releases it in the cooler. Without it the airend would overheat within minutes.
- It seals. A thin oil film fills the micron-size clearance between the rotors — compressed air does not leak back and the compressor keeps its capacity.
- It lubricates and protects. Bearings and rotors run on an oil film; additives protect against corrosion, deposits and foam.
That is why oil is not just a running cost — it is the life insurance of the screw compressor airend.
2. What happens when the oil ages
High temperature and the oxygen in the air oxidise the oil over time: it darkens, its acidity rises, varnish and sludge appear. The consequences follow one another:
- Temperature rises — aged oil carries heat away worse and the compressor trips on high temperature;
- The separator clogs — pressure drop and energy use grow, oil carries over into the network;
- Bearings and rotors wear — this is an airend overhaul, which costs far more than many oil changes.
All of this is avoidable with the right oil and timely service.
3. Five oils for five duty profiles
All of these oils come from the Atlas Copco multi-brand line — top-quality lubricants designed for oil-injected screw compressors of any manufacturer. In other words, the same oil is compatible with all screw compressors; you do not have to look for a separate oil for each brand. The only difference is the duty: how many hours the compressor runs and in what conditions.
ROTAIR — standard oil, up to 2,000 hours. Mineral oil with detergent additives. Intended for compressors up to 30 kW in light duty, at a compressor-room temperature of 0–30 °C. A good choice for workshops and small production sites where the compressor runs a few hours a day.
ROTAIR PLUS — up to 4,000 hours. Premium mineral oil for compressors above 30 kW running 2,000–4,000 hours a year. Room temperature up to 35 °C. The change interval is twice as long as with a standard mineral oil.
ROTAIR Xtra — up to 8,000 hours. Synthetic oil on a PAO (polyalphaolefin) base — for any power rating, 24/7 operation and harsh conditions, at a compressor-room temperature up to 46 °C. The high viscosity index (133) means the oil keeps its properties in heat and cold, and it does not freeze down to −57 °C, so it starts without problems even in an unheated room in winter. According to the manufacturer, the interval is 8,000 hours or 2 years.
Food Grade — up to 4,000 hours. Synthetic oil with NSF H1 registration — approved where incidental food contact is possible. Intended for food and beverage production, pharmaceuticals and packaging; room temperature 0–30 °C.
Note: the temperatures above refer to the room where the compressor stands and draws its air from — not to the oil itself. Inside the compressor the oil normally runs at 80–95 °C, and all of these oils are made for that. But the hotter the room, the hotter the oil: as a rule of thumb, every +10 °C of oil temperature roughly halves its service life. That is why, in a hot, poorly ventilated room in summer, the synthetic ROTAIR Xtra (up to 46 °C) is far more reliable.
ROTAIR Gear — for oil-free compressors, up to 8,000 hours. In an oil-free screw or tooth compressor the oil never enters the compression chamber — the air stays clean, and the oil lubricates only the gearbox and bearings. That needs a different, more viscous oil: ROTAIR Gear is a premium mineral oil with high-performance additives, viscosity ISO VG 68. Interval: 8,000 hours on compressors up to 55 kW and 16,000 hours above 55 kW; compressor-room temperature 0–50 °C. See oil-free screw compressors.
The four oils for oil-injected compressors (ROTAIR, PLUS, Xtra, Food Grade) are all ISO VG 46 (46 mm²/s at 40 °C) — the standard grade for oil-injected screw compressors. Which of them suits your compressor we select together, by running hours and conditions.
4. Compressor oil change: hours, environment and age
A compressor oil change is planned by the hours stated for the oil, but those hours are the maximum interval under normal conditions. The interval gets shorter with:
- Heat in the compressor room — the oil oxidises faster (see how to protect a compressor in summer);
- Dust and dirty intake air — the air filter does not stop everything and particles get into the oil;
- Humidity, frequent start-stops and short cycles — the compressor never fully warms up and water collects in the oil (see winter maintenance for air systems).
Three rules that always apply:
- Hours or age — whichever comes first. Oil also ages while standing, so even in a rarely used compressor it is changed on time.
- Change the oil filter with the oil. New oil in an old, dirty filter loses its life. The air filter and separator are changed per the manufacturer’s schedule or by pressure drop.
- Signs the oil must be changed early: strong darkening or a burnt smell, foam, milky oil (water), rising temperature or oil consumption.
5. How to choose the oil — in one table
| Your situation | Oil | Interval | Why |
|---|---|---|---|
| Oil-free screw or tooth compressor (gearbox) | ROTAIR Gear | 8,000 / 16,000 h | VG 68, room up to 50 °C |
| Food, beverage, pharma, packaging | Food Grade | up to 4,000 h | NSF H1 — safety and audit requirements |
| 24/7 operation, hot room, 4,000+ h a year | ROTAIR Xtra | up to 8,000 h | Fewer stops, works up to 46 °C |
| Above 30 kW, 2,000–4,000 h a year | ROTAIR PLUS | up to 4,000 h | Balance of price and interval |
| Small compressor, a few hours a day | ROTAIR | up to 2,000 h | Economical for light duty |
6. What a compressor oil change really costs
Oil is not judged by its price per litre. In 8,000 running hours a 2,000-hour oil is changed 4 times, a 4,000-hour oil twice, the synthetic 8,000-hour oil once. Every change also means an oil filter, a compressor stop and a service visit. In a plant running 24/7, one hour of downtime often costs more than the oil — that is where synthetic oil pays off. In light duty, where the compressor does not even reach two thousand hours a year, a standard mineral oil is perfectly sufficient.
7. Five mistakes that shorten oil life
- Mixing oils. When mineral and synthetic oils, or oils from different makers, are mixed, the additives can clash — foam and deposits appear. When changing oil type, the system must be flushed.
- Topping up with “whatever is at hand”. Engine or hydraulic oil does not go into a compressor — it has different additives and properties.
- Ordinary oil in food production. Where the air touches the product you need H1 oil and the right filtration (see the ISO 8573-1 air purity configurator).
- Changing the oil without the filter. The old filter contaminates the new oil straight away.
- “Stretching” the interval. A 2,000-hour oil will not last 4,000 hours — saving on oil ends with an airend overhaul.
Frequently asked questions
How often should compressor oil be changed?
A compressor oil change is due according to the oil grade — every 2,000, 4,000 or 8,000 running hours, or by age (whichever comes first). Heat, dust and humidity shorten the interval.
Can I switch from mineral to synthetic oil?
Yes — for a compressor running 24/7 it is often the most profitable change. When switching, the system must be flushed and the oil filter replaced — we do this during a service visit.
Is Food Grade oil only for food production?
It works in any oil-injected screw compressor, but it is needed most where the air touches the product or packaging — food, beverages, pharmaceuticals.
Which compressors are these oils for?
All oil-injected screw compressors — the Atlas Copco multi-brand oils are designed for compressors of any manufacturer. We choose the grade (ROTAIR, ROTAIR PLUS, ROTAIR Xtra or Food Grade) by the duty.
Does an oil-free compressor need oil too?
Yes — not in the compression chamber, but the gearbox and bearings need oil. ROTAIR Gear (ISO VG 68) is used there and changed every 8,000–16,000 hours.
What pack sizes are available?
The oils are produced in 5, 20 and 209-litre packs. Contact us for current availability.
Conclusion
Choosing the right oil and a timely compressor oil change come down to three questions: how many hours a year the compressor runs, in what conditions (temperature, dust, humidity) and whether the air touches food. Light duty is covered by the standard mineral ROTAIR, a 24/7 plant saves with the synthetic ROTAIR Xtra, and the food industry needs Food Grade. The key is to change on time and together with the filter.
Not sure which oil suits your compressor? Send us the model and running hours — we will select the oil and plan the service: ☎ +995 577 11 20 02, [email protected]. Compressor oils → · Compressor service →
