Pressure Washer Debate: Detergent vs. ND Oil

[jake88]

I've been looking everywhere for pump oil recommendations and it seems that almost everyone recommends or markets a non-detergent oil for triplex plunger pumps. Other than the typical warning ("Never use motor oil or other detergent oil"), it does not seem that there is a whole lot of why these pumps would require non-detergent oil. So here is the big question I have: Does anyone have a good explanation of why these pumps require non-detergent oil and specifically recommend against detergent-containing oils?

It would seem to me that in an environment like this one where water contamination is expected, sump sizes are small and equipment is moved frequently, that an oil with high levels of dispersants and corrosion inhibitors would protect equipment better than ND products. A water-in-oil emulsion would lubricate better than pure water, which you might expect to encounter if you had a oil-water phase separation in a splash lubricated crank. Not to mention that some of the most effective petroleum-based rust and corrosion inhibitors are detergents.

So again, what is the reasoning??

 

[BrocLuno]

I'd run Rotella T6 and not look back. Cheap enough and check it often

I agree with your logic. I have run motor oil all sorts of equipment and most of it is still running 25~50 years later. I usually ready the warnings, but did not have dedicated hydraulic oil on hand, so HDEO went in and prolly did not come out for a few years ...

 

[901Memphis]

The additives will emulsify in the water if it gets in the oil, so having more additives here will actually hurt you.

 

[demarpaint]

IIRC the reason is the detergents hold dirt and wear metals in suspension so a filter can filter it out. Since there's no combustion and no filter, SA non-detergent oil is better suited. So I just buy 30 grade non-detergent oil and use that. It's easy enough to find. OTOH there are people who use detergent oil and claim they have no problems. I'll stay with non-detergent since I can easily get it.

If you're getting water in your pump oil you have a bad seal somewhere, and the additives will do more harm than good. You shouldn't be getting any water in the pump oil, if you are ND oil is better. I'd check the seals.

 

[jake88]

This isn't a piece of equipment I own or have even used. Generally, I recommend people use detergent over non-detergent in small, mobile sumps because it emulsifies water and reduces the chance of free water being sucked or splashed onto load zones where lubrication is required. Many people recommend ND for those applications, but the biggest use of ND oils in hydraulic and gear are very large units where residence time in the reservoir is long enough for water to settle to the bottom of the reservoir and be drained through the drain valve.

You do bring up an interesting point with the seals. Are you familiar with the seal materials used in these types of pumps? I would imagine it is regular NBR, but would the seal conditioners present in a formulated dispersant oil offer other advantages over commonly available SA oils?

 

[Kestas]

Originally Posted By: demarpaint
IIRC the reason is the detergents hold dirt and wear metals in suspension so a filter can filter it out...

This is my understanding as well.

 

[Revving2Redline]

I thought those took 30HD Non Detergent.Sold a MITM when I worked at Sherwin Williams and it took 30wt IIRC.

 

[901Memphis]

Here's an older relevant discussion

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1920826

 

[bubbatime]

8th post in and I'll answer the big question for you, since no one else has.

Detergent oil has a tendency to foam when used in these kinds of pumps. As you are aware, foam is mostly molecules of air, which does not lubricate as well as oil and can cause galling, metal on metal contact, and basically cause the pump to overheat and fail. DO NOT USE DETERGENT OIL!!

I use regular ol SuperTech non-detergent SAE30 oil, readily available at Wal-Mart for $2.XX per quart.

You are welcome to buy and use pressure washer pump oil which is about $10 per quart. I change the oil frequently enough where I just use the cheap $2 per quart stuff. Works fine and has worked fine for years.

The more expensive stuff will have certain additives that the ND oil doesn't have but will be safe for pumps and will not foam. I used Cat pump oil extensively in the past, but now I just use the cheap stuff, which I have found to work just fine.

https://www.walmart.com/ip/Super-Tech-Non-Detergent-SAE-30W-Lubricating-Oil-1-qt/52626201

 

[440Magnum]

In situations where a lot of water intrusion into the oil sump is expected (like air compressors and pressure washers), its generally better to have an oil that doesn't contain dispersants that emulsify the oil and water. Its better to let the water stay separate and fall to the bottom of the sump until its time for an oil change to get rid of it.

 

[BrocLuno]

So let me get this straight, the anti-foaming agents in modern oil do not work, but plain base oil will foam less and work better?

 

[dave123]

I second the recommendation for CAT pump oil and it is the only oil that I will use.

 

[440Magnum]

Originally Posted By: BrocLuno
So let me get this straight, the anti-foaming agents in modern oil do not work, but plain base oil will foam less and work better?


No. The emulsifiers in modern oils DO work, but when there's a whole lot of water and not much heat, you really do not want to emulsify all the oil into a milkshake. Its better to let the water remain separate.

 

[jake88]

Originally Posted By: 440Magnum

No. The emulsifiers in modern oils DO work, but when there's a whole lot of water and not much heat, you really do not want to emulsify all the oil into a milkshake. Its better to let the water remain separate.



I imagine these systems have very small oil sumps, the machines move around a lot and I gather that they are typically splash lubricated. That is not a set of conditions that would allow the water to separate much whether you use ND or detergent oil. I would think that emulsified water-in-oil would be better than the alternative. Also SA oil has no corrosion inhibitors, which I would want if I knew there would be water.

I still haven't seen a really compelling answer to the question. Foam may be an issue - the emulsion may not release air as well as SA oils that are not emulsified. However, modern engine oils (for example) undergo air release tests which I would think closely mimic the action of splash-lubricated cranks in these pumps.

 

[440Magnum]

Originally Posted By: jake88
I would think that emulsified water-in-oil would be better than the alternative. .


I can't think of any possible reason why emulsified oil would be a benefit. It changes viscosity so it doesn't even splash very well anymore (basically turns to a gel).

Also, the proper oils for compressors and pumps aren't really "non-detergent," they have a particular set of anti-wear, anti-corrosion, and cleaning additives that are intended to work without turning the oil into a frappe. I don't think true "non-detergent" (as in 1930's style) oil is what anyone would recommend here. But the last thing you want is an ENGINE oil with all its dispersants and additive package components that are optimized for a very different environment.

 

[CharlieJ]

What about some regular 75w-90 gear oil, how well would that work in the pump? Anyone use it?

 

[jake88]

Many water-in-oil emulsions are used as lubricants in oilfield and industrial applications.

How much water are we talking about getting into these sumps - 10%? More? I can't imagine that much water is sitting happily at the bottom of the sump in these systems. If there is that much water, it's flying all over the place - on loaded parts. A water-in-oil emulsion is going to have better lubricity than free water.

 

[440Magnum]

Originally Posted By: jake88
Many water-in-oil emulsions are used as lubricants in oilfield and industrial applications.

How much water are we talking about getting into these sumps - 10%? More? I can't imagine that much water is sitting happily at the bottom of the sump in these systems. If there is that much water, it's flying all over the place - on loaded parts. A water-in-oil emulsion is going to have better lubricity than free water.



This is obviously different from a pressure washer applicaiton, but I can tell you for a fact that I can run my 2-cylinder air compressor, shut it down, and immediately drain the oil and the water comes out as separated blobs followed by the oil, not as chocolate pudding the way it would if engine oil were to be used in there.

Splash-lubed sumps don't generally have an oil pickup at the very bottom of the sump the way pressure-lubed systems do- they just churn the layer on the surface. A fair amount of water can definitely stay fairly well out of the action at the bottom of the sump.

 

[jake88]

Originally Posted By: 440Magnum
I can tell you for a fact that I can run my 2-cylinder air compressor, shut it down, and immediately drain the oil and the water comes out as separated blobs followed by the oil, not as chocolate pudding the way it would if engine oil were to be used in there.


Experience trumps speculation. I've never used one of these things, so if it works, I guess it works.