Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns. 

Frequently asked questions about air-cooled home standby generator oil

This article addresses frequently asked questions about oil for air-cooled home standby generators.

Environment

This article applies to residential air-cooled home standby generators.
 

FAQ

For model specific information consult your owner's manual. See Where can I find a user manual or other documentation for my home standby generator?
 

What does Motor Oil Do?

• It circulates through the engine to keep it cool and prevent wear by acting as a lubricant.  It helps prevent corrosion, keeps surfaces clean, and seals the engine.
• Synthetic oil is tailored for higher temperature and pressure.

What is the difference between Regular and Synthetic oil?  

• Both conventional and Synthetic oils are derived from petroleum but can be very different products.
• Conventional oil is refined from crude oil.
• Synthetic oil is also refined, but then it’s distilled and purified so that it contains fewer impurities.  It also contains additives intended to help keep engines cleaner and protect it from damage.
• Regular oil is more apt to pick up deposits and form sludge
• Synthetic oil has increased engine protection and performance at low and high temperatures.

What type of oil should I use in my home standby generator and what oil does it come with? 

• The specific type of oil recommended varies depending on the run hours.
  
• Residential air-cooled standby generators are shipped with 5W-30 conventional oil for use during the break-in period, after which Generac’s proprietary synthetic 5W-20 Gaseous Engine Oil (GEO) is recommended.

Note: For more detail, see: What type of oil should I use in my home backup generator?

How often should I change the oil in my generator?

• Oil change intervals vary based on usage patterns, climate, and total run hours; refer to the maintenance schedule for specific guidelines. See Where Can I Find the Maintenance Schedule for My Generac Home Standby Generator?

How do I check the oil level in my generator? 

• See How Do I Check the Oil Level in My Home Standby Generator? for a step-by-step guide. 

What happens if the generator runs out of oil?

• What Does It Mean When My Generator Displays an Error Code: Low Oil Pressure, Code 1300?

Can I keep adding oil when running low without doing an oil change?

• Definitely top off oil levels in an emergency low-oil situation, but ALWAYS follow the required service maintenance intervals in the manual.
• When adding new oil to bring oil levels back to normal, the old, sludgy, dirty oil doesn’t disappear – It just mixes with the new, fresh, clean oil. This puts more stress on the new oil and keeps it from working as well as it could.

Can I mix different brands or types of oil in my home standby generator? 

Example: If I normally use a 5W-30 non-synthetic or Generac’s proprietary synthetic 5W-20 Gaseous Engine Oil (GEO), can I add a 5W-30 synthetic?  What if my Generator is running low and that’s all I have available during an outage?
 

It is not recommended to mix oils; however, in an emergency outage situation when no alternative exists, it is possible to mix oil for limited emergency use. Mixing different types of oil will not harm your engine in the short term, but it is important to perform a full oil change as soon as possible. Most oils are compatible with each other because many are a blend of natural and synthetic oils.  

Mixing Motor Oil

• It’s always better to stick to one grade of oil till you decide to change your oil completely.

Possible Negative Effects

• It’s recommended to not mix two different brands of oil as the additives may or may not be compatible.
• The additives in synthetic oil may have limited or no effect when mixed with regular engine oil.
• Mixing different synthetic oil blends could actually have negative effects in the long term as the additives may react.

 

See If My Generator Has Been Running 5W-30 Synthetic Oil, Can I Switch Over to Conventional? for additional information. 

What do I do if I overfill the oil in my generator?

• Overfilling can cause damage to the engine. If you have overfilled the oil, drain the excess until you reach the correct level indicated on the dipstick. 

How much oil does a generator typically need?

Oil capacity varies by unit. Exact capacity specifications can be found in the owner's manual and specifications sheet.
See the following articles for more information.

• How Do I Find My Generator's Product Manuals, Parts Lists and Spec Sheets in Mobile Link?
• What is the oil capacity of a home standby generator?