ISO 46 vs. ISO 68: Choosing the Right Oil for Your Rotary Screw Air Compressor in Canada

Rotary screw air compressors power a wide range of industries across Canada—from manufacturing facilities in Ontario to agricultural operations on the Prairies. To keep these compressors running efficiently and reliably, choosing the right oil is one of the most important maintenance decisions you can make.

One of the most common questions operators face is: Should you use ISO 46 or ISO 68 compressor oil?

Each viscosity grade behaves differently, especially in Canada’s diverse climate. Below is a clear breakdown to help you select the right lubricant for your rotary screw air compressor.

Why Compressor Oil Matters More Than You Think

Rotary screw compressors rely on oil not only for lubrication but also for:

• Cooling the compression chamber

• Sealing internal clearances

• Reducing wear on rotors and bearings

• Preventing rust and oxidation

• Improving system efficiency

Using the incorrect oil viscosity can lead to overheating, excessive energy use, and premature component failure. That’s why matching the oil grade to your compressor and operating climate is essential.

ISO 46 and ISO 68: What’s the Difference?

The numbers 46 and 68 refer to oil viscosity at standard testing temperature.

• Lower number = thinner oil

• Higher number = thicker oil

Here’s what that means for your system:

ISO 46 Oil – Medium Viscosity

• Flows easily at lower temperatures

• Ideal for compressors operating in cooler environments

• Reduces drag, improving energy efficiency

• Suitable for lighter-duty or moderate-load applications

ISO 68 Oil – Higher Viscosity

• Provides a stronger lubrication film

• Better for high temperatures and heavy loads

• Reduces metal-to-metal contact in demanding conditions

• Often recommended for continuous-duty compressors

How Climate in Canada Affects Your Oil Choice

Canada’s climate varies significantly, and your region’s temperature plays a major role in selecting the right oil.

ISO 46 is typically preferred when:

• The compressor is located in a cooler climate (B.C. coast, Northern Canada, winter conditions)

• Indoor facilities stay below ~20°C

• Equipment experiences light to moderate load

• Quick cold-start performance is essential

ISO 68 is a better fit when:

• The compressor runs in hot environments (foundries, mechanical shops, summer heat waves)

• Operating temperatures regularly exceed 30°C

• The compressor runs continuously or at high load

• Extra protection against wear is required

Equipment Type and Usage Also Matter

Different compressors have different lubrication requirements. For example:

• High-duty rotary screw compressors benefit from ISO 68’s thicker protective film.

• Variable speed compressors may use ISO 46 to maximize efficiency.

• Older compressors often perform better with ISO 68 due to wider internal clearances.

Always check your manufacturer’s recommendation, then adjust based on your real-world operating environment.

Energy Efficiency Considerations

Thicker oil (ISO 68) can increase drag, causing the compressor to use more energy.Thinner oil (ISO 46) reduces energy consumption but may not provide enough protection under heavy load.

Choosing the correct viscosity ensures a balance between performance and power savings.

Signs You May Be Using the Wrong Oil

Watch for these performance issues:

• Excessive heat or shutdown warnings

• Increased oil carryover

• Loud or unusual rotor noise

• Shortened oil change intervals

• Slow startup in cold environments

If you see any of these symptoms, switching viscosity grades may improve performance.

MasterAire’s Recommendation for Canadian Industries

For optimal performance across varied Canadian conditions:

• ISO 46 is generally best for cooler climates and moderate workloads.

• ISO 68 is ideal for warmer environments, continuous operation, and heavy-duty applications.

MasterAire offers high-quality synthetic and semi-synthetic compressor oils designed specifically for rotary screw compressors operating in North America. These oils resist oxidation, extend service life, and enhance overall system reliability.

Final Thoughts

Selecting the right oil—ISO 46 or ISO 68—is crucial for protecting your rotary screw air compressor, improving efficiency, and prolonging equipment life. By considering your climate, workload, and compressor type, you can make a choice that keeps your system running smoothly year-round.

If you need help choosing the correct oil for your specific compressor model, MasterAire’s support team is here to assist you with expert guidance and product recommendations.