ISO 68 vs ISO 100 vs ISO 150 Natural Gas Compressor Oil

ISO 68 vs ISO 100 vs ISO 150 Natural Gas Compressor Oil

ISO 68, ISO 100, and ISO 150 are common viscosity grades used in compressor oil.

But if you are buying oil for a natural gas compressor, viscosity is only part of the decision.

A compressor handling natural gas, CNG, RNG, landfill gas, methane, wet gas, or another hydrocarbon gas stream may expose the oil to gas dilution, heat, pressure, moisture, heavy hydrocarbons, or other contaminants. That means two oils with the same ISO grade may not perform the same way in natural gas compressor service.

This guide explains the difference between ISO 68, ISO 100, and ISO 150 natural gas compressor oils, and what to check before ordering.

What Does ISO Grade Mean in Compressor Oil?

ISO grade refers to the oil’s viscosity classification. In simple terms, it tells you how thick or thin the oil is at a standard test temperature.

A lower ISO grade, such as ISO 68, is lighter than ISO 100 or ISO 150. A higher ISO grade, such as ISO 150, is heavier than ISO 68 or ISO 100.

That matters because viscosity affects oil film strength, flow, lubrication, heat transfer, and how well the oil can protect moving parts under load.

But viscosity grade does not tell the whole story.

Why ISO Grade Alone Is Not Enough

ISO grade tells you how thick the oil is. It does not tell you whether that oil is suitable for natural gas compressor service.

Natural gas compressors may expose the lubricant to gas interaction. Depending on the compressor design and gas stream, hydrocarbon gas can dilute the oil and reduce its working viscosity.

That is why a standard ISO 100 air compressor oil and an ISO 100 oil intended for natural gas compressor service should not automatically be treated as interchangeable.

Before ordering, confirm both:

• The required ISO viscosity grade
• Whether the oil is appropriate for the gas compressor application

ISO 68 Natural Gas Compressor Oil

ISO 68 is a lighter viscosity grade compared to ISO 100 and ISO 150. It may be used in select natural gas compressor applications where the equipment manufacturer or maintenance program calls for ISO VG 68 oil.

ISO 68 may be considered in applications where the compressor design, temperature, pressure, and lubrication point require a lighter oil. However, it should not be selected simply because it flows more easily or appears on a product list.

For natural gas compressor applications, confirm that the ISO 68 oil is suitable for the gas stream and operating conditions.

Common checks for ISO 68 oil:

• Does the OEM call for ISO VG 68?
• Is the oil suitable for natural gas or hydrocarbon gas service?
• Is the compressor handling clean gas, wet gas, CNG, RNG, or landfill gas?
• Is the oil used in a gas-exposed area?
• Are pressure and temperature within the oil’s intended operating range?

ISO 100 Natural Gas Compressor Oil

ISO 100 is a common viscosity grade in industrial compressor applications, including some natural gas compressor systems.

It may be used in certain rotary screw, reciprocating, CNG, pipeline, gas gathering, or industrial gas compression applications depending on the equipment and service conditions.

Because ISO 100 is common, it is also easy to choose too quickly. The phrase “ISO 100 compressor oil” does not automatically mean the oil is right for natural gas service.

Common checks for ISO 100 oil:

• Does the equipment require ISO VG 100?
• Is the compressor handling air or natural gas?
• Is the oil intended for gas compressor service?
• Is the gas stream clean, wet, sour, or heavy with hydrocarbons?
• Does the OEM recommendation mention a specific oil type or performance requirement?

ISO 150 Natural Gas Compressor Oil

ISO 150 is heavier than ISO 68 and ISO 100. It may be used in more demanding compressor applications where the equipment calls for a heavier viscosity grade.

ISO 150 may appear in certain reciprocating gas compressors, rotary screw gas compressors, CNG compressors, RNG systems, landfill gas applications, pipeline equipment, and other industrial gas compression environments.

Heavier oil can help support oil film strength in certain operating conditions, but that does not mean ISO 150 is automatically better. Too heavy can be wrong just like too light can be wrong.

Common checks for ISO 150 oil:

• Does the OEM call for ISO VG 150?
• Is the compressor operating under higher pressure or heavier load?
• Is the gas stream wet, dirty, or heavy with hydrocarbons?
• Is the oil used in cylinders, packing, rotors, or another gas-exposed area?
• Does the oil match the compressor type and service condition?

Quick Comparison: ISO 68 vs ISO 100 vs ISO 150

The right viscosity depends on the compressor and application, but this simple comparison can help frame the decision.

This table is a starting point, not a substitute for the OEM recommendation.

How Gas Conditions Affect Viscosity Choice

Natural gas compressor oil does not operate in a clean little fantasy world where nothing weird happens.

The gas stream can change the way the oil behaves.

Clean Natural Gas

Clean natural gas may place less contamination stress on the oil than wet gas or landfill gas, but the oil still needs to match the compressor and OEM recommendation.

Wet Gas

Wet gas may include moisture, condensate, or liquid hydrocarbons. These can affect oil life, lubrication performance, and viscosity stability.

Heavy Hydrocarbons

Heavy hydrocarbons may dilute the oil and reduce working viscosity. In these applications, the oil’s performance in gas service matters as much as the viscosity number on the label.

RNG and Landfill Gas

RNG and landfill gas applications may involve variable gas quality, moisture, contaminants, or corrosive compounds. These conditions require careful oil selection and should be checked against OEM requirements.

Compressor Type Affects Oil Choice Too

The same ISO grade may be used differently depending on the compressor design.

Reciprocating Gas Compressors

Reciprocating gas compressors use pistons and cylinders to compress gas. Oil selection may depend on whether the lubricant is used in the frame, cylinders, packing, or another lubrication point.

Because some lubrication points may be exposed to the gas stream, viscosity and gas-service suitability both matter.

Rotary Screw Gas Compressors

Rotary screw gas compressors use two rotating screws to compress gas. In oil-flooded designs, the oil may interact more directly with the gas stream.

This makes oil stability and gas dilution resistance important, especially in natural gas, CNG, RNG, or landfill gas applications.

Centrifugal and Other Gas Compressors

Centrifugal compressors, rotary vane compressors, gas boosters, and other compressor types may have different lubrication requirements. Always match the oil to the equipment design and OEM recommendation.

ISO Grade vs Application Category

A better way to choose oil is to think in two layers.

Layer 1: Viscosity Grade

This answers: how thick should the oil be?

• ISO 68
• ISO 100
• ISO 150
• ISO 220 or other grades when required

Layer 2: Application Suitability

This answers: is the oil built for the environment?

• Natural gas compressor service
• CNG compressor service
• RNG or landfill gas service
• Wet gas or heavy hydrocarbon exposure
• Reciprocating or rotary screw compressor design

You need both layers. Viscosity without application suitability is only half the answer.

What to Check Before Ordering by ISO Grade

Before choosing ISO 68, ISO 100, or ISO 150 natural gas compressor oil, confirm the details that actually determine compatibility.

1. OEM Recommendation

Start with the compressor manufacturer’s recommendation. Confirm the viscosity grade, oil type, and any application-specific notes.

2. Compressor Type

Identify whether the compressor is reciprocating, rotary screw, centrifugal, rotary vane, rotary lobe, gas booster, or another design.

3. Gas Stream

Confirm whether the compressor handles natural gas, CNG, RNG, landfill gas, methane, wet gas, sour gas, or another hydrocarbon gas stream.

4. Gas Condition

Determine whether the gas is clean, wet, dirty, sour, or heavy with hydrocarbons.

5. Lubrication Point

Confirm whether the oil is used in the frame, cylinders, packing, oil-flooded compression chamber, bearings, or another lubrication point.

6. Operating Pressure and Temperature

Pressure and temperature influence oil film strength, dilution behavior, oxidation, and oil life.

7. Packaging Needs

If you are buying for a compressor station, CNG refueling site, RNG facility, landfill gas system, or multiple compressors, consider whether pails, drums, totes, or bulk ordering make sense.

Buying Larger Quantities of ISO Compressor Oil

Natural gas compressor applications often use more oil than small shop-air systems. Compressor stations, CNG sites, gas gathering systems, RNG facilities, and multi-compressor operations may need larger quantities for maintenance planning.

Depending on the product and availability, options may include pails, drums, totes, or bulk ordering.

Final Takeaway

ISO 68, ISO 100, and ISO 150 all describe viscosity grades. They do not automatically confirm whether an oil is right for natural gas compressor service.

Start with the OEM recommendation, then confirm the compressor type, gas stream, gas condition, lubrication point, pressure, temperature, and application requirements.

In natural gas compression, the right question is not just “What ISO grade do I need?” It is “What ISO grade do I need for this compressor, this gas stream, and this operating environment?”