Generator owners have reported observing milky-colored oil when performing maintenance on their generators.

Environment

This article applies to air-cooled standby generators. 

Cause

The presence of "milky" or light brown colored oil is often the result of humidity in the air accumulating in the oil due to the generator running frequently with no load. Running without a load means the engine does not reach temperatures sufficient to burn off condensation.

How do I manage this?

If you live in an area with high humidity, or in a place where your generator may be exposed to higher than typical moisture levels from blowing snow or other environmental factors, we recommend running the generator under load on a monthly basis. The best way to do this is to simulate a power outage: How Do I Simulate a Power Outage to Test My Home Standby System?

• Run the generator under load (powering circuits in your home) for 30 minutes. Start timing after power transfer to your generator occurs.
• Running your generator under load allows the engine to build up to a higher temperature.

This process will evaporate any excess moisture that may be present within the engine. Keep in mind that when a generator performs its scheduled exercise cycle, it is not under load. Longer exercise cycles, or running the generator with no load will not significantly reduce moisture that may be present, as the engine does not get hot enough during the exercise cycle to fully evaporate excess moisture.

Note: Owners of Next Generation series generators with a Premium Mobile Link subscription can use the exercise with power transfer command to run the generator under load: Using the "Exercise Now" and "Exercise now and transfer power" commands in Mobile Link

Additionally, we recommend:

• Performing regular oil changes per the generator's maintenance schedule: Where Can I Find the Maintenance Schedule for My Generac Home Standby Generator?
• Change the exercise schedule to bi-weekly or monthly exercise to reduce the amount of time the generator is running at no-load: How Do I Set the Scheduled Generator Exercise Date and Time?

Will this damage my generator?

Generac support has not received any reports of mechanical issues from normal amounts of moisture or condensation, as the water vapor boils off when the engine heats up while running under load.

High quality oil, like our premium 5W-20 GEO oil (part number A0001412864), will trap the moisture in an emulsion and take on a “milky” appearance. This is preferred, as it means that the moisture present is not pooled up in the bottom of the engine, and will easily boil off once the engine warms up and the oil circulates.