Generac Oil Capacity Chart by kW, with Oil Type and Change Interval
For a current Guardian or Next Generation unit, the answer is Generac's own 5W-20 full synthetic "gaseous engine oil" — part A0001412874 per quart — API SJ, SL or better, no additives. New units ship with 5W-30 conventional for the 25-hour break-in (20 hours on the 7.5 kW PowerPact); Generac's break-in article names A0001412874 for that first change and every change after. Capacities with the filter: 10 kW Guardian 1.1 qt; 14/18 kW 2.2 qt; 20–26 kW 1.9 qt; Next Generation 10 kW 1.4 qt, 14/18 kW 2.5 qt, 22–28 kW 2.2 qt; PowerPact 1.2 qt. Interval after break-in: every 2 years or 200 hours (Schedule A), dropping to every 100 hours when it runs below 40 °F or continuously above 85 °F. Older units have different viscosity charts — they're below, by generation.
Generac oil capacity chart by kW
Find your generator line and kilowatt rating. Capacity includes the filter and is approximate: Generac prints "Approx." on every figure, and you fill to the dipstick's FULL mark rather than to the number. Current Next Generation and Guardian units take 5W-20 gaseous engine oil after break-in; older manuals specify synthetic 5W-30, and PowerPact and EcoGen print a chart by temperature.
| kW | Generator line | Engine | Oil capacity with filter (as printed) | Oil type (as printed) | Source (document, page) |
|---|---|---|---|---|---|
| 10 | Next Generation (2025+) | G-Force 400, 459 cc | Approx. 1.4 qt (1.3 L) | After the 25-hour break-in, "Generac's proprietary 5W-20 gaseous engine oil (GEO)"; API SJ, SL or better | Owner's manual A0004332577 Rev. C, pp. 14, 28; spec sheet A0005151081 Rev. D, p. 4 |
| 14, 18 | Next Generation (2025+) | G-Force 800, 817 cc | Approx. 2.5 qt (2.4 L) | Same as above | Owner's manual A0004332577 Rev. C, pp. 14, 28; spec sheet A0005151081 Rev. D, p. 4 |
| 22, 24, 26, 28 | Next Generation (2025+) | G-Force 1000, 997 cc | Approx. 2.2 qt (2.1 L) | Same as above | Owner's manual A0004332577 Rev. C, pp. 14, 28; spec sheet A0005151077 Rev. D, p. 4 |
| 10 | Guardian (2023 manual) | G-Force 400, 460 cc | Approx. 1.1 qt (1.03 L) | After the 25-hour break-in, "Generac's proprietary 5W-20 gaseous engine oil (GEO)"; API SJ, SL or better | Owner's manual A0001846499 Rev. C, pp. 9, 24 |
| 14, 18 | Guardian (2023 manual) | G-Force 800, 816 cc | Approx. 2.2 qt (2.1 L) | Same as above | Owner's manual A0001846499 Rev. C, pp. 9, 24 |
| 20, 22, 24, 26 | Guardian (2023 manual) | G-Force 1000, 999 cc | Approx. 1.9 qt (1.8 L) | Same as above | Owner's manual A0001846499 Rev. C, pp. 9, 24 |
| 10 | Guardian (2020 manual) | G-Force 400, 460 cc | Approx. 1.1 qt (1.03 L) | "Synthetic SAE 5W-30 for all temperature ranges"; API SJ, SL or better | Owner's manual A0000973303 Rev. A, pp. 11, 27 |
| 14, 18 | Guardian (2020 manual) | G-Force 800, 816 cc | Approx. 2.2 qt (2.1 L) | Same as above | Owner's manual A0000973303 Rev. A, pp. 11, 27 |
| 20, 22, 24 | Guardian (2020 manual) | G-Force 1000, 999 cc | Approx. 1.9 qt (1.8 L) | Same as above | Owner's manual A0000973303 Rev. A, pp. 11, 27 |
| 13, 16 | Guardian, models G007173–G007178 (2019 spec sheet) | G-Force 800, 816 cc | Approx. 2.2 qt / 2.1 L | Not printed on the spec sheet | Spec sheet 10000033190 Rev. A, p. 4 |
| 9 | Evolution era (2016 manual) | GH-426, 426 cc | Approx. 1.1 qt (1.03 L) | "Synthetic SAE 5W-30 for all temperature ranges"; API SJ, SL or better | Owner's manual 0L6629 Rev. A, pp. 7, 25 |
| 11 | Evolution era (2016 manual) | GTH-530, 530 cc | Approx. 1.7 qt (1.6 L) | Same as above | Owner's manual 0L6629 Rev. A, pp. 7, 25 |
| 16, 20, 22 | Evolution era (2016 manual) | GT-999, 999 cc | Approx. 1.9 qt (1.8 L) | Same as above | Owner's manual 0L6629 Rev. A, pp. 7, 25 |
| 20 (three-phase) | 20 kW three-phase (2017 manual) | G-Force 1000, 999 cc | Approx. 1.9 qt (1.8 L) | "Synthetic SAE 5W-30 for all temperature ranges"; API SJ, SL or better | Owner's manual 10000003882 Rev. C, pp. 6, 21 |
| 15 | EcoGen | GT-999, 999 cc | Approx. 3.75 Quarts / 3.55 Liters | "SAE 30 above 32 ºF (0 ºC)"; "SAE 10W-30 between 40 º and -10 ºF (4 º and -23 ºC)"; "Synthetic SAE 5W-30 for all temperature ranges" | Owner's manual 0K6046 Rev. F, pp. 7, 23 (Internet Archive copy of Generac's own URL) |
| 7.5 | PowerPact | GA-420, 420 cc | Approx. 1.2 qt (1.1 L) | "SAE 30 above 32 ºF (0 ºC)"; "SAE 10W-30 between –10 ºF (4 ºC) and above"; "Synthetic SAE 5W-30 for all temperature ranges" | Owner's manual 10000021790 Rev. C, pp. 8, 22 |
Read the engine column before the kW column. A 16 kW unit from the 2016 manual has a 999 cc engine and takes about 1.9 qt; a 16 kW unit on the 2019 spec sheet has an 816 cc engine and takes about 2.2 qt. The same kilowatt rating, two different answers. The PowerPact middle line is quoted exactly as Generac printed it, including its temperature pairing. Not in the chart, because no Generac document we could reach states it: 8, 12 and 17 kW units, Nexus-era units before 2013, and liquid-cooled models. Use the manual for your model number.
Other brands: Honda, Champion, Predator, Westinghouse, DuroMax and Cummins Onan oil specifications are in the generator oil type and capacity finder.
What oil Generac specifies
Generac's oil FAQ is short and unusually direct. New home standby units ship with 5W-30 conventional oil for the break-in period. After break-in, Generac recommends its "proprietary synthetic 5W-20 Gaseous Engine Oil (GEO)" for ongoing use. The reasoning it gives: conventional oil "is more apt to pick up deposits and form sludge," while synthetic "contains additives intended to help keep engines cleaner" and offers "increased engine protection and performance at low and high temperatures." Mixing conventional and synthetic is not recommended but acceptable in an emergency — if you do, "perform a full oil change as soon as possible."
The current 10–26 kW owner's manual adds the standard that any substitute has to meet: "All Generac oil kits meet minimum American Petroleum Institute (API) Service Class SJ, SL, or better," and "do not use special additives." "Gaseous engine oil" means what it says — a formulation Generac specifies for its natural-gas and propane engines.
The one case where Generac tells you to use something else: a unit that hasn't reached 25 hours after a full year. Its break-in article gives two options — run the unit under load in MANUAL to reach 25 hours, or change the oil to "5W-30 conventional oil (not synthetic)" as a temporary measure until the break-in hours are reached. That is the only official endorsement of conventional 5W-30 outside the factory fill.
Why oil capacity does not follow kilowatts
Capacity follows the engine, not the rating, so a smaller unit can take more oil than a bigger one. Every figure includes the filter. Fill to the dipstick's FULL mark, not to the number: Generac warns that "Overfilling can lead to increased pressure within the engine, which can cause leaks and damage to engine seals and other components."
Two things to notice. First, capacity does not scale with kilowatts — the 14/18 kW twins take more oil than the 20–26 kW engines. Buying "two quarts for a 22 kW" leaves you with a spare; buying two for a 14 kW leaves you short by a splash. Second, the viscosity spec has moved: the 2016 9–22 kW manual, the 2017 three-phase manual and the 2020 revision of the 10–24 kW manual all specify "Synthetic SAE 5W-30 for all temperature ranges," and the 2023 revision moved to 5W-20 GEO. The newer oil is not wrong in an older engine, but the manual for your serial number is the document a warranty claim is judged against.
Nexus-era units (pre-2013) are not in the chart, and that is deliberate. Generac no longer publishes the owner's manual for the 8/10/14/17/20 kW Nexus generation on its own site, and a search of the Wayback index across generac.com, dam.generac.com and Generac's manual-file service found no archived copy of it either. Every version circulating online sits on a retailer or a document reseller, and this site does not take figures from those. If you have a Nexus unit, the manual that came with it is the document to use for oil grade and capacity, and a dealer can look the figures up against your serial number.
Portable, inverter and pressure-washer models take different oil
If you have a GP, XG or iQ portable, or a Generac pressure washer, stop before you buy 5W-20 GEO — Generac's own support article says explicitly that the 5W-20 gaseous engine oil is for home standby units running on natural gas or propane, not for portables. Portables are gasoline engines and take ordinary automotive-grade oil chosen by temperature.
Generac's portable viscosity guidance is a three-way chart: above 32 °F, "SAE 30 oil is recommended"; between −10 °F and 40 °F, "10W-30 oil"; and "Synthetic 5W-30 oil can be utilized in all temperatures for added convenience." The manuals give the same three options with an operating range of −18 °C (0 °F) to 40 °C (104 °F). Break-in is petroleum-based oil first — the GP Series manual says "Use petroleum based oil (supplied) for engine break-in before using synthetic oil."
Generac portable generator oil capacity by model
| Model | Oil capacity | Break-in change | Routine interval | Source |
|---|---|---|---|---|
| GP3300i | 0.6 qt (0.6 L) | First month or 20 hours | Every 100 hours or 6 months | Manual A0001141434 Rev. B |
| GP3600 (212 cc) | 0.63 qt (0.6 L) | — | — | Spec sheet 10000036668 Rev. E |
| GP6500 / GP6500E / GP8000E | 1.06 qt (1.0 L) | 30 hours | Every 100 hours or yearly | Manual 10000029705 Rev. C |
| GP15000E / GP17500E | 1.7 qt (1.6 L) with filter; 1.4 qt (1.3 L) without | 25 hours | Every 200 hours or yearly | Manual 0H0676A Rev. C |
| iQ3500 | 0.6 qt (0.6 L) | First month or 20 hours | Every 100 hours or 6 months | Manual 10000033207 Rev. A |
| GP6700EDF (dual fuel) | 0.95 qt (0.9 L) | 30 hours | Every 100 hours or yearly | Manual A0005966335 Rev. A |
| GP9500ETF (tri fuel) | 1.16 qt (1.1 L) | 30 hours | Every 100 hours or yearly | Manual A0005966335 Rev. A |
Note the GP15000E and GP17500E: 200 hours, double the interval of the rest of the line, and the only portables here with an oil filter to account for in the capacity. Generac's general portable guidance — change after the first 20 to 30 hours, then every 100 hours — is a summary, and the two big-frame units are the exception to it.
Models we deliberately left out of the table. We could not obtain a Generac-hosted manual or spec sheet stating oil capacity for the GP3300 (the non-inverter model — it is a different machine from the GP3300i and the 0.6 qt figure does not transfer), the XG series including the XG8000E, or the legacy 4000XL and 5500. Generac's own maintenance-kit sheet confirms the XG8000E uses a 407 cc engine while the GP8000E uses a 420 cc engine, so carrying the GP figure across would be wrong. If you own one of these, the capacity is on the decal or in the manual that shipped with the unit; we would rather leave a gap than print a number we cannot source.
Generac pressure washer oil
Same viscosity chart, much shorter intervals, and no capacity published. Generac's pressure-washer manual states "Climate determines proper engine oil viscosity. See chart to select correct viscosity" — SAE 30, 5W-30 or 10W-30 — and adds two practical notes: "Below 50°F (10°C) use of SAE 30 will result in hard start," and "Above 80°F (27°C) use of 10W30 may cause increased oil consumption."
The break-in is aggressive: "First 5 Hours: Change engine oil." After that the two official manuals disagree, and the disagreement is real rather than an error on our part — manual A0001468710 Rev. D says "Every 20 Hours or Every Year: Change engine oil," while manual 0K8031 Rev. D (models 009045 and 009073) says every 50 hours or every year. Use the interval in your own manual.
One thing not to do: the pump is not a maintenance item. "DO NOT attempt any oil maintenance on pump. Pump is lubricated and sealed at factory. No additional maintenance is required for life of pump."
Honeywell-branded standby generators
Honeywell-branded home standby generators are widely reported to have been Generac-built, which is why searches for Honeywell generator oil land on Generac specifications. We could not source that manufacturing relationship to a Generac or Honeywell document, so treat it as background rather than as a spec: use the manual that shipped with your unit, and if it is a rebadged Generac the viscosity and capacity tables above will match it.
Change intervals
- Break-in: 25 hours (20 hours on the PowerPact 7.5 kW), oil and filter — Generac's article says "no earlier, no later." Metal particles in that first drain are normal. Valve clearance is inspected at the same service, except on 14 and 18 kW Guardians and Next Generation units with hydraulic lifters.
- Schedule A: every 2 years or 200 hours, whichever comes first — oil and filter, plus a battery inspection. The controller lights the yellow LED and shows SERVICE A when it's due.
- Extreme temperatures: every 100 hours. Generac's Schedule A article and the owner's manual agree: units operating below 40 °F or continuously above 85 °F need oil and filter every 100 hours (the manual says "every year or 100 hours"). A unit that ran through a week-long winter outage has likely used most of that.
- Schedule B: every 4 years or 400 hours — oil and filter again, plus air filter, spark plugs and valve clearance. That's what the maintenance kit is for.
- The intervals have moved less than people assume. The 2016 manual (0L6629 Rev. A) and the 2017 three-phase manual (10000003882 Rev. C) both give Schedule A as "Every Two Years or 200 Hours" and Schedule B as "Every Four Years or 400 Hours" — the same figures as the current manual. What did change is the oil itself: both of those manuals specify "Synthetic SAE 5W-30 for all temperature ranges," where the 2023 manual moved to 5W-20 GEO. Read your own manual's table rather than assuming the older schedule was tighter.
- During a long outage: check daily. Generac's oil-level article says to check the level every day while the unit is running an extended outage. A 1300 Low Oil Pressure shutdown in the middle of a storm is the alternative.
How to check and change the oil
Checking, per Generac's article: set both the utility main and the generator's MLCB to OFF; if the unit was running, let it run five minutes with no load, then cool five to ten minutes; pull the dipstick, wipe, reinsert fully, read; add to FULL, never above. Clear the yellow maintenance reminder afterwards if one was showing — on Evolution units, press ENTER when the reminder is displayed, arrow to YES, ENTER; the maintenance timer resets itself.
Changing it is inside most owners' reach, and Generac sells the kits on that assumption. The sequence that Generac's post-maintenance article expects you to finish with: reminder cleared, panels reinstalled, the 7.5 A fuse back in, Install Wizard completed if the controller asks, AUTO pressed (green light), MLCB ON, lid closed. If you're doing it during an outage, run one minute with the MLCB OFF before switching it ON.
Generac's oil-filter article identifies the filter for your serial number (070185ES in the current 10–26 kW manual). The parts table below has the oil; the filter and everything else are on the maintenance-kit page.
Parts and consumables
| Part | Part number | Fits | Where verified |
|---|---|---|---|
| 5W-20 full synthetic GEO, 1 qt | A0001412874 | All current air-cooled home standby | Generac break-in maintenance article |
| 5W-20 full synthetic GEO, case of 12 qt | A0001412864 | Same | Dealer listing (Gensys Parts) |
| 5W-20 full synthetic GEO, case of 12 qt (alternate listing) | A0001412868 | Same | Dealer listing (The Modern Shop) |
You may see "0J5993" quoted online as a Generac oil part number. No Generac or dealer listing under that number could be found; the quart is A0001412874. Oil filter numbers vary by engine and are listed with the kits on the maintenance kit page.
As an Amazon Associate we earn from qualifying purchases. Links open Amazon in a new tab; prices and availability are shown there, never here.
Keep two quarts of A0001412874 on the shelf — enough for one change on any Guardian, with a top-up left for a long outage.
- Generac 5W-20 full synthetic GEO, 1 quart (A0001412874), 2-pack Matches the oil the current air-cooled maintenance kits ship with.
- Generac 5W-20 full synthetic GEO, case of 12 (A0001412864)Find on Amazon
- Generac full synthetic 5W-30 (0J5323A), 5 qt For the models whose manual specifies 5W-30 for all temperatures.
- Full synthetic 5W-30, 5 qt (any brand meeting the spec) Valvoline SynPower (ASIN B00GZKC6DS); the manual specifies a viscosity, not a brand.
Repair or replace?
Not a question here — oil is the cheapest thing you will ever put in this machine, and the low-oil-pressure shutdown on every air-cooled model exists because running it dry is the most expensive. The relevant version of the question: a unit that has gone several years past Schedule A and now knocks or smokes has earned an inspection before the next outage, not just an oil change.
When to call a dealer
- You're not sure which generation your unit is — the serial-number lookup on Generac's site or a dealer settles the viscosity question.
- Oil level rises between checks, or the oil smells of fuel — a fuel-system fault, not an oil question.
- The unit has crossed 400 hours without a valve-clearance service and you don't own a feeler gauge.
- Milky oil — water intrusion; the manual's yearly inspection exists for this.
- Generac support: 1-888-436-3722.
Related pages
Everything else in a Schedule B service — filter, plugs, air filter, kit numbers by model: Generac maintenance kit. The other wear item: battery replacement. The shutdown that low oil causes: code 1300 — and every other code the controller can show, with the reset sequence for each, is on the Generac error code hub. A generator from another brand: the generator oil type and capacity finder looks up Honda, Champion, Predator, Westinghouse, DuroMax and Cummins Onan models from their own manuals.
Not sure the generator can carry the load?Generator Wattage Calculator Running watts, the largest starting surge, and a generator class from manufacturer charts.Frequently asked questions
What kind of oil does a Generac generator take?
Current Guardian and Next Generation units: Generac 5W-20 full synthetic gaseous engine oil (A0001412874), API SJ/SL or better, no additives. Evolution-era units specified synthetic 5W-30 for all temperature ranges. For Nexus-era units (pre-2013) no figure is given here, because Generac no longer publishes that manual and the copies circulating online are all on retailer or reseller sites.
Can I use regular 5W-30 in my Generac?
Generac ships new units with 5W-30 conventional for break-in and, in its break-in article, allows 5W-30 conventional temporarily on a unit that hasn't reached 25 hours in a year. For ongoing use it recommends its 5W-20 synthetic GEO; mixing is acceptable only in an emergency, followed by a full change.
How many quarts of oil does a Generac 22 kW take?
Approximately 1.9 quarts (1.8 L) including the filter, per the owner's manual for 20–26 kW Guardians. Fill to the dipstick's FULL mark rather than to the number.
How often should I change the oil in a Generac standby generator?
First at 25 hours (break-in), then every 2 years or 200 hours (Schedule A). Below 40 °F or in continuous heat above 85 °F, every 100 hours. Check the level daily during an extended outage.
Is synthetic oil required in a Generac?
Generac recommends it and its kits contain it. The manuals' hard requirement is API SJ, SL or better with no additives; the synthetic recommendation is about deposits and temperature range.