Kohler · REOZ Series (Diesel Commercial Standby)

Kohler 40REOZK

40 kW standby / 36 kW prime · Diesel · Liquid-cooled

40 kW diesel commercial standby generator. Kohler-powered diesel for commercial, healthcare, education, and government standby applications.

Kohler Kohler 40REOZK generator — specifications and details
Standby power
40 kW / 36 kW prime
Voltage options
120/208V, 277/480V, 120/240V
Frequency / Phase
60 Hz · 1/3-phase
Engine
Kohler KDI 3404TM · 3.4L
CommercialHealthcareGovernment
Configure & QuoteDownload spec sheet

Overview#

The Kohler 40REOZK is a 40-kilowatt diesel commercial standby generator powered by a Kohler diesel engine at 1800 RPM. It serves commercial facilities, healthcare, education, and government applications where diesel fuel independence is required. The unit features a 4-pole rotating-field alternator with PowerBoost excitation, low coolant level shutdown protection, and is available with weather-protective and sound-attenuated enclosures rated for 186 mph wind loads.

Our service experience#

OnPoint services Kohler REOZK diesel generators across Northern California. The 40REOZK is a popular choice for mid-size commercial buildings and medical offices, and we typically structure maintenance around an annual PM with semi-annual fuel quality checks.

Engineering specifications

Physical

Length
90.6 in
Width
41 in
Height
44.5 in
Wet weight
1,735 lb

Fuel system & runtime

Fuel use @ full load
3.7 GPH
Fuel use @ 75% load
3.1 GPH
Fuel use @ 50% load
2.4 GPH

Photos

Kohler 40REOZK — product photo

Documents & downloads

Spec sheets & manuals

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Configure your Kohler 40REOZK

Lock the enclosure, fuel system, transfer switch, and add-ons — we'll confirm pricing, availability, and lead time within one business day. Prefer a free-form quote? That option is still here.

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Estimate runtime for the Kohler 40REOZK

Adjust load percent and tank size to estimate runtime. Pre-filled with this model's spec where available.

Estimate runtime on this tank

Estimated runtime

70.1 hours(2.9 days)

Fuel consumption ≈ 2.85 GPH at 75% load. Estimate based on industry-typical 1800 RPM standby curves (≈0.07 GPH/kW at full load). Actual consumption varies by engine, ambient temperature, fuel quality, and tuning.

Service intervals

Manufacturer-recommended intervals for the Kohler 40REOZK under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.

Oil & filter
Every 250 hours or 12 months
Coolant change
Every 2000 hours
Air filter
Every 500 hours
Fuel filter
Every 250 hours
Major overhaul
≈ 8,000 hours
Load bank test
Every 12 months

Common failure modes

What we've seen fail on this platform. Use as a service-planning reference, not a diagnostic — actual failure modes depend heavily on duty cycle and maintenance history.

ComponentSymptomTypical hoursSeverity
Fuel quality / degradationInjector fouling, hard starting, reduced power output4,380+moderate
Coolant thermostatOvercooling at light load, extended warmup time8,000+minor
Battery (starting)Slow crank, failed exercise, low voltage alarm8,760+minor

Frequently Asked Questions

What engine is in the Kohler 40REOZK?
The 40REOZK uses a Kohler diesel engine rated at 1800 RPM, EPA certified for stationary emergency standby use.
Is there a Tier 4 Final version of the 40REOZK?
Yes. The 40REOZK4 is the EPA Tier 4 Final variant, certified for both stationary emergency and non-emergency applications.

Compatible equipment

Engine

Transfer switches

More in the REOZ Series (Diesel Commercial Standby)

Kohler's diesel commercial standby series — 10 to 510 kW, John Deere and Kohler engines, built for life-safety loads.

View all 33models in this series →

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