Is Motor Oil OK In Your Pressure Washer Pump?

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Pressure washers are indispensable machines for homesteaders who want to maintain high standards of cleanliness in their homes. From hard-to-clean driveways to stubborn stains on your car’s exterior, a pressure washer is all you need to dump your old cleaning rag and detergent. However, when it comes to taking care of these machines, a question many people often ask is whether motor oil is ideal for pressure washer pumps or not.

The truth is that motor oil is not suitable for pumps in power washers. The motor (engine) and pump require different types of oil. You don’t want to risk using the wrong pump oil and grind the inner workings of your machine to a halt. And while you can clean the pump and fill it with new oil, you will have a complex situation to handle should you use pump oil on the motor. You should also note that depending on the temperature of your locale, the kind of oil usable on the pressure water pump varies. 

For those who prefer synthetic oils to regular ones, take note of their unique properties. Some lubricants are suited to specific machines. From our end of the bargain, the best advice we can give regarding the use of motor oil on pressure washer pumps is that you should check the user manual for directions. Manufacturers do indicate pump oil suitable for your pressure washer. Are you a car wash operator or a homesteader looking to put money on a good power washer? Well, this post walks you through everything you need to know about lubricating the pump so keep reading to learn more.

Why lubricate pressure washer pump?

An obvious argument is that movable parts in a machine require lubrication to run smoothly. In this case, pumps in gasoline-powered pressure washers require regular lubrication for optimal functioning. Electric variants do not need oiling. Moreover, taking note that pumps are the workhorses in pressure washers, keeping them in great working condition is necessary.

Lubrication is one of the pillars of mechanics, especially design elements. Engineering graduates will tell you that a lecture on the type of oil suitable for different machine components takes at least two weeks for each component. Thus, oiling pumps in pressure washers is something you should care about because of the following reasons:

Improves the performance of pumps

Typically, oiling pumps improves its performance. Failing to lubricate pressure washer pumps is, therefore, a recipe for wear and tear. You should notice overheating as soon as oil in the pump becomes less useful due to contamination. An ideal lubricant ensures smooth gliding of pumps against nearby components so that it draws water into the washer and pumps it via the nozzle at high pressure.

Lubrication is a requirement for meeting warranty terms and conditions

Some manufacturers are very strict when it comes to meeting their warranty obligations. In the case of pressure washers, you should check the user manual for details. Will the manufacturer void the warranty if you fail to lubricate moving parts such as pump and motor? The truth is that it is easy to spot dirty oil, so you don’t want to let your pressure washer burn-out due to lack of regular lubrication.

Lubrication ensures longevity

When it comes to the care and maintenance of machines such as power washer pumps, lubrication is the key to the longevity of your machine. When a dry pump glides over nearby components, there is increased wear and tear. It means you will replace the pump sooner than necessary. Wear and tear is a necessary evil in machines but lack of oiling speeds it up, pushing up the cost of maintenance.

It is costly rebuilding/repairing pressure washer pumps

Failing to lubricate the pump in your power washer puts the component at risk of burn-out. The damage might be beyond repair. We bet you don’t want to tread the path of negligence. But let’s state that you will have little to worry about if lack of lubrication dirties the un-loader valve. All you will do if that is the case is to access the pump and clean it. Moreover, it is easy to repair damaged o-rings and seals due to lack of lubrication. However, problems with swash plates and pistons are a little advanced, usually occasioning a complete pump overhaul.

What is the difference between motor and pump oil?

The differences between oil for pressure washer motor and pump are their properties. For those who have dug deeper into this subject, you already know that additives give lubricants varying properties.  You will note that silicon compounds are common in pump oils. Their role is to guard against foaming. On the other hand, motor oil contains detergents such as magnesium sulfonate. Thus, you may ask, what do these variations signify? Well, we researched the differences and discovered the following:

Detergent vs. non-detergent oils

Detergent oils serve to clean the inner surfaces of a motor. A filter then removes contaminants so that they don’t get to ball bearings. It means that most, if not all modern motors, have an oil filter and work best with detergent oils. The absence of a filter would mean oil gets dirty fast hence the more frequent you should replace it. Non-detergent oils are suitable for pumps in pressure washers. It is because they do not have oil filters. Lubricating pumps with detergent oils, therefore, poses a risk of wear and tear due to faster contamination.

Non-foaming vs. non-aeration oil additives

It is important to use anti-aeration and anti-foaming additives in pump oils. Aeration often leads to vibration/undesirable chattering and in the process, making the oil less viscous. Highly viscous oil due to aeration is not effective on movable pressure washer components like the water pump. Thus, most pump oils have anti-aeration additives.  And when it comes to foaming of oil in the pump, it can cause pressure or oil leaks.

Oil labeling as a distinguishing characteristic

When you go shopping for pump oil, look for the labeling ND, which stands for non-detergent. Also, look for the words ‘pump oil.’ Any oil labeled ‘classic cars,’ usually dating back to the early ’90s is ideal for pressure water pumps. The catch is that cars manufactured in the 1920s or earlier used non-detergent oils because they did not have oil filters.

Always look for labeling such as 15W 40, SAE 30. The begging question is what do they mean to a novice homesteader looking for pressure pump oil? Well, it is all about viscosity. Take, for example, SAE 20 which means the oil flows easily compared to SAE 40 under the same conditions. In cases when you come across labels such as SAE15 W 40, it denotes multi-viscosity. The first value (15) signifies ease of flow in low temperatures while the second one (40) is the viscosity at high temperatures.

When to change pump oil in your pressure washer

Typical residential pressure washer pumps are permanently sealed hence no need for oil replacement. In the case of pump failures, replacement is, therefore, the ideal thing to do instead of repair. You should read the user manual to ascertain the ideal measures. However, most power washers in the market today have pumps that require regular lubrication. You can call it an oil change.

Thus, regardless of the model or brand of your pressure washer, pump maintenance is crucial because of the reasons we explored earlier. Now, when it comes to figuring out the frequency of changing oil, let’s state the following:

  • Use a dipstick to check the oil level in the pump to determine if changing it is necessary. You should replace the oil that is darker, milky and has particles. The fact is that you should stick to non-foaming, non-aeration and non-detergent pump oils with elements that inhibit rusting.
  • We advise that you change pump oil 10 hours after the first use, usually at the start of spring. The catch is that oil in power washer pumps thicken during winter and not changing it at the start of a new season poses risk to the health of the component.
  • You should always read the user manual and learn more about maintenance tips on pressure pumps. Most manufacturers state the frequency of changing pump oil, which is important to novice craftsmen.
  • The next time you should change oil is after every 250 hours of using the machine. It is a golden rule for most manufacturers. It translates to quarterly (3 months) frequency. It also applies to motor oil in pressure washers.  

Final Thoughts

The bottom line is that motor oil is not suitable for pressure washer pumps. Because pumps do not have oil filters hence risk damage due to impurities in motor oils, always use non-detergent oils.  And when it comes to replacing used lubricant that has become less viscous, do not overfill the pump. An oil leak is the worst problem you want to deal with, let alone damaged seals. Most importantly, stick to manufacturer’s instructions on the user manual which includes safe disposal of used oil to a recycling plant. You would rather be safe than sorry.