Before you begin. This procedure is general reference information, not professional advice. Equipment varies by manufacturer, model, and year. Always follow the documentation supplied with your equipment — where it differs from this page, follow the manufacturer. Verify that you have the tools, the working conditions, and the ability to do this task safely. If anything is unclear, if the equipment is damaged, or if the task exceeds your experience, stop and use a qualified professional. You are responsible for your own safety and for the outcome. This site accepts no liability for any loss, damage, or injury arising from the use of this information.
Specifications marked unverified could not be traced to a manufacturer source. Do not rely on them — obtain the value from your equipment documentation.
Summary
A pressure washer has two engines' worth of oil to think about, and most owners know only one of them. The engine has its own oil, and the high-pressure pump bolted to it often has a separate oil of its own, sealed inside a small crankcase behind the wand connection. On many consumer machines, especially electric ones, that pump oil is sealed at the factory and is never meant to be opened. On others, mostly gas machines with a Triplex or plunger pump, the pump has its own fill point, drain plug and sight glass, and it needs its own oil changed on its own schedule. This page's first job is to help you work out which kind you own.
What this page will not print is a single oil grade, a single capacity, or a single change interval that is true of every machine, because the pump maker and the machine maker do not always agree, and sometimes only the pump maker publishes a number at all. Generac's own manual gives 50 hours and a non-detergent oil for the Triplex pumps in its own machines; Cat Pumps, a pump maker whose pumps are built into machines from other companies, gives a different interval and its own oil grade for its own pumps. If the oil in your sight glass or on your dipstick looks milky or white, this page stops with you and sends you to a service dealer, because that color change means water has already reached the crankcase.
Necessary equipment
| Item | Note |
|---|---|
| The documentation for your pump and your machine | The documentation names the oil grade and the interval for your pump. |
| Protective gloves | Wear the gloves before you drain the oil. |
| Eye protection | Wear eye protection before you release the water pressure. |
| A drain pan or a container | Use the container to catch the used oil. |
| A dry cloth | Use the cloth to clean the area around the dipstick. |
| A flashlight optional | Use the flashlight to see the level in the sight glass. |
| The oil grade approved for your pump material | Use only the grade that the documentation for your pump specifies. |
| A sealed, labeled container for the used oil material | Use the container to store the used oil for disposal. |
Find the type of your pump
Estimated 2 min to 4 min
- Look at the pump body for an oil fill point, a drain plug, or a sight glass.<1mReport a problem with step 1, Find the type of your pump
- A pump body with none of these parts has a maintenance-free design.
- Read the section about the pump in the documentation for your machine.1mReport a problem with step 2, Find the type of your pump
- Generac's own manual names a serviceable pump on its machines a Triplex pump.
- Some documentation names a maintenance-free pump an axial cam pump.
DO NOT OPEN A PUMP THAT HAS NO OIL FILL POINT, NO DRAIN PLUG, AND NO SIGHT GLASS.
Generac states that a maintenance-free pump needs no service for its life. If you open a maintenance-free pump, you can damage it.
- If the pump has no oil fill point, no drain plug, and no sight glass, stop this procedure.<1mReport a problem with step 3, Find the type of your pump
Prepare the machine before you work at the pump
Estimated 3 min to 6 min
SET THE MACHINE SWITCH TO OFF BEFORE YOU WORK AT THE PUMP.
REMOVE THE PLUG FROM THE SOCKET ON AN ELECTRIC MACHINE. An unexpected start can injure your hand.
- Set the machine switch to off.<1mReport a problem with step 1, Prepare the machine before you work at the pump
- If the machine is electric, remove the plug from the socket.<1mReport a problem with step 2, Prepare the machine before you work at the pump
- Close the water supply tap.<1mReport a problem with step 3, Prepare the machine before you work at the pump
POINT THE TRIGGER GUN AWAY FROM YOUR BODY AND OTHER PEOPLE BEFORE YOU SQUEEZE THE TRIGGER.
Water at high pressure can injure your skin.
- Point the trigger gun away from your body and from other people.<1mReport a problem with step 4, Prepare the machine before you work at the pump
- Squeeze the trigger to release the water pressure in the hose.<1mReport a problem with step 5, Prepare the machine before you work at the pump
- Engage the safety lock on the trigger gun.<1mReport a problem with step 6, Prepare the machine before you work at the pump
- If the machine has an engine, let it cool.2mReport a problem with step 7, Prepare the machine before you work at the pump
Do a check of the pump oil level and its condition
Estimated 4 min
- Place the machine on a level surface.<1mReport a problem with step 1, Do a check of the pump oil level and its condition
- Clean the area around the sight glass or the dipstick with a dry cloth.<1mReport a problem with step 2, Do a check of the pump oil level and its condition
- If your pump has a sight glass, read the oil level at its center.<1mReport a problem with step 3, Do a check of the pump oil level and its condition
- Cat Pumps names this an oil bubble gauge on the rear cover of the crankcase.
- If your pump has a dipstick, remove it.<1mReport a problem with step 4, Do a check of the pump oil level and its condition
- Clean the dipstick with a dry cloth.<1mReport a problem with step 5, Do a check of the pump oil level and its condition
- Insert the dipstick fully.<1mReport a problem with step 6, Do a check of the pump oil level and its condition
- Remove the dipstick again to read the oil level.<1mReport a problem with step 7, Do a check of the pump oil level and its condition
- Generac's own manual places the correct level between the L mark and the H mark.
- Look at the color of the oil against a light background.<1mReport a problem with step 8, Do a check of the pump oil level and its condition
STOP IF THE OIL IS MILKY OR CLOUDY.
DO NOT ADD OIL. DO NOT RUN THE MACHINE. Cat Pumps states that water in the oil is a sign of a worn seal in the pump.
- If the oil is milky or cloudy, stop this procedure.<1mReport a problem with step 9, Do a check of the pump oil level and its condition
- If the oil is clear and the level is low, add the oil that your documentation specifies.1mReport a problem with step 10, Do a check of the pump oil level and its condition
Drain and refill the pump oil
Estimated 5 min to 6 min
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
No tier-1 source was found for this value. Take it from the documentation supplied with your equipment.
- Read the oil change interval in the documentation for your pump.<1mReport a problem with step 1, Drain and refill the pump oil
- Generac gives 50 hours of operation for the Triplex pumps in its own machines.
- Cat Pumps gives an initial 50 hours, then every 500 hours after that, for its own pumps.
WEAR PROTECTIVE GLOVES AND EYE PROTECTION BEFORE YOU DRAIN THE OIL.
Used oil can irritate your skin and your eyes.
- Wear protective gloves and eye protection before you drain the oil.<1mReport a problem with step 2, Drain and refill the pump oil
- Place a container under the drain plug.<1mReport a problem with step 3, Drain and refill the pump oil
LET THE PUMP COOL BEFORE YOU REMOVE THE DRAIN PLUG.
Hot oil can burn your skin.
- Remove the drain plug.<1mReport a problem with step 4, Drain and refill the pump oil
- Let the oil drain fully into the container.1mReport a problem with step 5, Drain and refill the pump oil
- Install the drain plug. Tighten it by hand only.<1mReport a problem with step 6, Drain and refill the pump oil
- Clean the area around the oil fill point.<1mReport a problem with step 7, Drain and refill the pump oil
DO NOT FILL THE PUMP WITH OIL ABOVE THE MARK.
Cat Pumps states that too much oil can leak from the fill cap.
- Fill the pump with the oil grade that your documentation specifies.<1mReport a problem with step 8, Drain and refill the pump oil
- Generac specifies SAE 30 or 10W-40 non-detergent oil for the Triplex pumps in its own machines.
- Cat Pumps names its crankcase oil grade as ISO 68. Cat Pumps does not recommend another oil for its own pumps.
- Cat Pumps directs an owner who needs the fill quantity to its own Tech Bulletin 134.
- Fill the pump only to the mark on the dipstick or the sight glass.<1mReport a problem with step 9, Drain and refill the pump oil
- Install the dipstick or the fill cap by hand only.<1mReport a problem with step 10, Drain and refill the pump oil
- Clean up any spilled oil.<1mReport a problem with step 11, Drain and refill the pump oil
Dispose of the used oil
Estimated 2 min
DO NOT POUR USED OIL INTO A DRAIN OR ONTO THE GROUND.
Used oil can pollute the water supply.
- Pour the used oil into a sealed, labeled container.<1mReport a problem with step 1, Dispose of the used oil
- Take the container to a local collection point for used oil.1mReport a problem with step 2, Dispose of the used oil
Terminology
This page uses one term for each item and holds it throughout, as ASD-STE100 requires. Equipment sellers and other guides use the names below for the same parts.
- pressure washer pump
- Also called: power washer pump, jet wash pump, the pump on my pressure washer, washer pump head
- pump oil
- Also called: crankcase oil, pump crankcase oil, oil in the pump, hydraulic oil for the pump
- triplex pump
- Also called: plunger pump, piston pump, three-piston pump, pro pump
- maintenance-free pump
- Also called: sealed pump, axial cam pump, no-oil pump, factory-sealed pump
- sight glass
- Also called: oil bubble gauge, oil window, oil level window, bubble gauge
- milky oil
- Also called: cloudy oil, white oil, oil that looks like milk, water in the pump oil
- non-detergent oil
- Also called: pump oil without detergent, straight oil, non detergent oil
When to use a professional
Stop if the oil is milky or cloudy. Do not add oil. Do not run the machine. Water in the oil is a sign of a worn seal inside the pump. Speak to a service dealer for your machine.
Stop if the pump leaks oil after you refill it. Do not open the pump. A leak from a worn seal is not a home repair. Speak to a service dealer.
Stop if the pump has no oil fill point, no drain plug, and no sight glass. Do not open a maintenance-free pump. Speak to the maker of your machine if you are not sure which kind you own.
Stop if you cannot find the oil grade or the oil capacity for your pump. Do not guess the oil grade. The wrong oil can damage the seals inside the pump. Speak to the maker of your pump or your machine.
Speak to an electrician if the socket for an electric machine is wet or has damage. Do not use the machine until an electrician checks it.
Common questions
Does my pressure washer pump even have oil?
Some do and some do not, and there is no way to tell from the brand alone. Look at the pump body, the part the high-pressure hose screws into: a fill point, a drain plug or a small oil window is the sign of a serviceable pump. A smooth housing with none of those is a sealed, maintenance-free pump, and Generac's own manual is direct about it, telling the owner not to attempt any oil maintenance on a pump that is lubricated and sealed at the factory. Electric machines are the ones most often built this way: the manual for the Sun Joe SPX3000, an electric machine, carries no pump oil section at all. If you are still not sure, the documentation for your machine will say.
What oil goes in a pressure washer pump?
It depends entirely on who made the pump, and this page will not guess for you. Generac's own manual specifies SAE 30 or 10W-40 non-detergent oil for the Triplex pumps in its own machines. Cat Pumps, whose pumps are built into machines from other companies, specifies its own ISO 68 crankcase oil and states that it does not recommend the use of any alternative oils. Read the documentation for your own pump, not only your machine, because the two are sometimes made by different companies.
My pressure washer pump oil looks milky or white. What does that mean?
It means water has reached the crankcase. Cat Pumps explains the mechanism: once the low-pressure and high-pressure seals wear, water can travel back along the plunger rod and past the oil seal, and that water is a contaminant that can damage the drive-end components inside the pump. This is not a level you top up or a color you run past. Stop, do not add more oil, and do not run the machine again until a service dealer has looked at the seals.
How do I read the pump oil sight glass?
Cat Pumps calls it an oil bubble gauge, and it sits on the rear cover of the pump crankcase. The target is the center of the gauge, not the top: Cat Pumps says an overfilled gauge spits oil out of the red fill cap, which will not harm the pump but should still be drained back down. A dipstick is read the way an engine dipstick is read: remove it, clean it, insert it fully, then remove it again and read the mark. Generac's own manual places the correct level between the L mark and the H mark on its Triplex pump dipstick.
How often should I change the pump oil?
There is no single number that is true of every pump, which is why this page does not print one. Generac's own manual gives 50 hours of operation for the Triplex pumps in its own machines. Cat Pumps gives an initial 50-hour period, then every 500 hours after that, for its own pumps. Read the interval in the documentation for your own pump, because a pressure washer's hour meter, if it has one, is the most reliable way to track it.
Can I use regular motor oil in my pressure washer pump?
The documentation for the pumps checked for this page says no. Generac specifies a non-detergent oil for its own Triplex pumps, and non-detergent is the operative word: automotive motor oil carries detergent additives that a small, low-volume pump crankcase is not designed around. Cat Pumps goes further for its own pumps and states that it does not recommend any alternative oil at all. If the documentation for your pump names a specific product, that product is the safe choice, not a generic equivalent.
Related procedures
- How to winterize a pressure washer pump before freezing weather, and what to put in it
- How to use the soap or detergent injector on a pressure washer, and why nothing comes out of it
- How to check your engine oil and work out what oil your car takes
- How to choose the right pressure washer nozzle for the surface you are cleaning, and what the colours actually mean
- Clear a blocked pressure washer nozzle and inlet screen
- Check an automatic transmission fluid level, or establish that the transmission is sealed and has no dipstick
- What does the oil pressure warning light mean, and is it the same as the low oil light?
- Inspect a pressure washer hose, couplings and O-rings before use
Sources
Every specification on this page is traced to one of these sources. Tier 1 is a manufacturer document, a published standard, or a government safety authority. See Standards for the full tiering rule.
- Tier 1Small Pro Power Washer Owner's Manual (document G0069240, covers 3200-3600 PSI gas pressure washer models)
- Tier 1Oil Inquiries (Cat Pumps customer FAQ: oil grade, the bubble gauge, the change interval, and why the oil turns milky)
- Tier 1Lubrication — Genuine Cat Pumps Lubricants (product literature: crankcase oil grade and part numbers)
- Tier 1Sun Joe SPX3000 Electric Pressure Washer Operator's Manual (MR15, 06272023)
Revision history
Current version 1 · updated 2026-08-04 · next review due 2027-08-04
- v1 · 2026-08-04First draft. Two tier-1 pump/machine manufacturer documents were read directly (Generac's Small Pro Power Washer owner's manual PDF, fetched and extracted with pdftotext; Cat Pumps' own oil-inquiries FAQ and lubrication pages, fetched as static server-rendered HTML) plus one already-registered manual (Sun Joe SPX3000) re-read to confirm it carries no pump-oil section. Oil grade, oil capacity and oil change interval publish as consult-the-documentation instructions with no digit in them, because the pump maker and the machine maker are sometimes different companies and neither this site's manufacturer sources for Generac's own Triplex pumps nor for Cat Pumps' own pumps agree on a single number true of every machine; the specific per-maker figures are attributed by maker in step substeps and the FAQ, never promoted to a verified specification. The milky-oil diagnostic and the sealed-pump boundary both trace to a tier-1 pump manufacturer quote. Two support.generac.com/s/article/ pages were fetched during research and are NOT cited: a direct curl fetch of that Salesforce Experience Cloud host returned an empty JavaScript shell with no article text embedded, so their content could not be independently confirmed by reproducible means, and CLAUDE.md rule 9/6 treats a source that cannot be read as not a source. The PDF manual and the two static catpumps.com pages were used instead because both were independently re-fetched and their text verified byte-for-byte outside of any AI-mediated summary.
Corrections to this page are listed in the public corrections log. Reports that are credible and not yet verified are listed in the public errata register, and an open one renders above the step it concerns.
Comments and corrections
Found an error? A correction with a manufacturer source is applied and logged publicly. You can also write to corrections@fixchecklist.com.
Every step above carries its own report control, which tags the report with that step so a correction reaches the right place. For anything about the procedure as a whole — the order of the sections, a step that is missing, something that did not match your equipment — use this: report something about this whole procedure.