Engines used in Generac generators

Generac generators use two types of engines: the OHV (Overhead Valve) and OHVI (Overhead Valve Industrial).

• OHV: A general small-engine design used across many products. These engines are typically basic-duty with splash lubrication and no automotive spin-on oil filter—good for intermittent use and regular maintenance intervals.
• OHVI: Generac’s proprietary “industrial” OHV family, purpose-built for generator duty (long, continuous runtimes). Key upgrades include full-pressure lubrication and an automotive-style spin-on oil filter for longer life and heavier-duty operation. Many OHVI units have been produced in Wisconsin.

Which engines are paired with which generators?

• All air-cooled home standby generators (except the 7.5kW PowerPact) are built with OHVI engines.
• A majority of portable generators feature OHV engines. Larger portables, like the GP15500 EFI will feature the OHVI engine.
• See your generator's spec sheet and user manual to verify which engine is used.

OHV (Overhead Valve)

• Generac designed and assembled overseas
• No oil filter (will require more frequent maintenance)
• Splash lubrication - Internal engine action splashes oil on moving parts
• Mechanical governor - Not as quick to respond as an isochronous governor
• Rated for 1,000 hours with proper maintenance

OHVI G-Force (Overhead Valve Industrial) 

• Manufactured in Whitewater, WI
• Featured on all 9-28 kW air-cooled units (engine size matches power rating of generator, see below)
• Pressurized lubrication - Oil is pumped directly to critical areas
• Incorporates both an air filter and a spin-on automotive-style oil filter
• Electronic (Isochronous) Governor - Fastest responding governor available. Maximizes engine performance and virtually eliminates stalling
• Up to 3,000-hour rating with proper maintenance
• Next Generation Air-Cooled Standby models (459cc, 817cc, 997cc) feature hydraulic lifters, eliminating the need for valve adjustments

Engines used in the Next Generation Air-Cooled Standby Generator

Guardian series engines

Guardian series, liquid cooled, and portable engines

The OHVI 460cc engine is used in 10kW and 9kW liquid propane (LP) natural gas (NG) generators.


The OHVI 816cc engine is used in 14kW and 18kW natural gas (NG) and liquid propane (LP) generators.


The OHVI 999cc engine is used in 22kW LP/19.5kW NG, 24kW LP/21kW NG. 26kW LP/22.5kW NG generators.

OHV engines are used in a majority of portable generators and have a range of sizes.

Where can I get parts for my Generac generator engine? 

• Some generator parts are available on Generac's OrderTree site
• Parts manuals can be found by searching your generator's model or serial number using the Product Search tool on Generac.com
• If you can't find the part you are looking for, contact your local Generac authorized service dealer for assistance: How Can I Find a Generac Service Dealer in My Area?