Many people see lubricants and grease as an afterthought.
A nice-to-have to prevent squeaking and rust.
This couldn’t be further from the truth.
Lubrication is as important to mechanical engineering design as screws, welding, bearings, gears, clutches, brakes, couplings, flywheels, shafts and axles.
In my university Mechanical Engineering Design textbook, lubrication has its own chapter – taking up 6% of the 958-page Seventh Edition. It comes after rolling-contact bearings and before gears.
How big do you think the lubrication industry is?
It’s huge. The global market for lubricants was more than $55 billion USD in 2015. And it’s growing…
…With this amount of consumer spending, massive lubricant and grease company marketing spending follows. The marketing competition is fierce and gives you mixed messages, is confusing and creates too many choices of lubricating grease.
Let’s dive right in to find out.
Jump to each section:
- Lubrication Basics
- Silicone Grease Common Uses
- Safety of Silicone Lubricant
- Why Lubricate Your Rubber O-rings?
- Silicone Spray Can vs. Grease vs. Oil
- Which Tube You Should Buy
- How to Apply and How Often to Re-apply
1. Lubrication basics (and why silicone lubricant is best for rubber o-rings)
Is there a difference between calling a lubricant: lube, lubricant, grease or oil?
People tend to use all interchangeably. For this article we consider lube, lubricant and grease the same and oil as different.
Here’s the main difference. At room temperature:
- Grease has high viscosity (like peanut butter).
- Oil has lower viscosity (like vegetable oil).
Grease lubricant is used on parts that will operate at low speed and normal temperature.
Oil lubricant is used on parts that operate at high speed and temp.
What is the point of lubrication?
All types of lubrication – including oils, greases, and sometimes water or air – are used to reduce wear by reducing friction and heating of parts that move. Any substance that achieves this can be called a lubricant.
General characteristics to consider when deciding which form of lubrication is best:
- Stability. You want a lubricant to maintain its consistency when performing its role of reducing friction and heating between moving parts. If it tends to get harder or softer when working, it is said to be unstable.
- Temperature effects. What happens to the lubricant (grease or oil) at different temperature? Grease doesn’t perform well at high temps because it can’t get rid of the heat like oil can. At low temperature grease hardens and can clog up parts and prevent them from moving.
- Water resistance. Depending on the use, you will want lubricant to have a certain amount of water resistance to continue working normally even if water is there.
- Pumping ability. Most plants that operate machinery will have some form of automated grease dispensing system. These systems pump grease through lines and nozzles to the parts that need grease. This method saves money. Some lubricant won’t move through lines under pressure so its pumpability is important.
- Consistency. Ranging from fluid (canola oil) to normal grease (peanut butter) all the way to solid (cheese), the National Lubrication Grease Institute (NLGI) has a classification charts for grease consistency. Getting the lubrication to where it is needed and having it not leak out is critical – so a greases consistency is important during selection.
What is a lubricant made of?
There are different lubricant grease types for different purposes. All greases share a similar anatomy and are made from 3 basic pieces:
Classifying the different grease types
In the above chart you can see that a lubricant is made of mostly base oil (mineral or synthetic) with a thickener (fatty acid plus a soap alkali) to hold the base oil and additive package (usually graphite/molybdenum to improve temperature stability, performance under extreme pressure etc.) together.
The most common way to classify a mineral base oil grease is by its thickener: lithium grease, sodium grease… But when it comes to synthetic base oil grease it is classified by that: silicone grease etc…
What is each type best used for?
This is a loaded question because it is impossible to answer without knowing the exact conditions the lubricant will be used in. A conveyor belt pulley’s bearings operating in extreme heat in Australia will require different lubrication than if it was in extreme cold in Northern Canada.
With that being said, here’s the gist:
Mineral oil lubricants are used when there is a constant running temperature. Synthetic base oils are better over a wide range of conditions.
- Lithium is most common and used for bearings.
- Calcium for low temp bearings and bearings with water nearby (pumps).
- Sodium best for high temp bearings.
- Aluminium best oxidation resistance and best for back-and-forth moving parts like elevator drives and vibrating screens.
Additives are added to increase or suppress positive or negative properties of the base oil. Graphite or Molybdenum might be added to increase stability under high temp and pressure. Others are used to suppress oxidative qualities and increase corrosion resistance. Anti-foaming additives are added to most engine oils.
Why silicone lubricant grease is the best type for rubber o-rings and seals
Most O-rings are made from synthetic rubbers. Namely: nitrile, EPDM and Neoprene. It is true that petroleum products will degrade natural rubber. But if an o-ring is made from, nitrile, for example (a material used in car fuel and oil lines) then there is no problem using petroleum grease to lubricate the o-ring.
The problem is: How do you know if the o-ring is made from synthetic rubber or ordinary natural rubber? It is impossible to tell just by touching it, looking at it. And most User Manual’s will not tell you the material of the o-rings and seals. It might tell you it’s rubber – but synthetic or natural rubber?
The solution is: Use silicone lubricant for o-rings and seals to be safe. Silicone lubricant is waterproofing and lubricating. It costs $10 for a small tube and is available at all auto parts stores. Be safe, use silicone grease on your o-rings and rubber seals in pressure washer wands, hoses and pumps.
2. Five common uses for synthetic silicone oil based lubricant grease
The uses of silicone lubricating grease are nearly endless, but here are five of the most common:
Scuba gear and underwater devices
Divers use silicone grease to seal and protect dry suit gaskets. Spear-fisherman use it to protect their speargun rubbers and keep them supple. Snorkelers and swimmers use it in their underwater flashlights seals and to keep their underwater camera case seals from drying out.
When watchmakers or tinkerers are putting together the watch, silicone grease is used on the gaskets to aid reassembly and help prevent them tearing.
Silicone lubricant is so common in plumbing that it is often just called plumber’s grease. Whether it be faucet fittings, o-rings, water filter housing threads
Fountain and other pen enthusiasts and repair professionals love to take apart and tinker with their often expensive pens. In the process they come into contact with latex sacs, rubber seals & o-rings and ebonite (hard rubber) pistons/feeds/barrels. Upon reassembly 100% silicone lube is used to seal and protect everything and make it easier to put together.
Pressure washer pump and hose o-rings and threads
Professional power wash contractors use lube on hose connections and o-rings to make installation easier and to protect the o-ring from damage. It is also used during pump repair and assembly to help install the unloader valve.
3. How safe silicone based lubricants are for use around your home, garage and job-site
There are two types of silicone grease: safe and food grade safe.
Food grade silicone lubricants are approved for safe use in equipment and parts that may have contact with food in production, processing, packaging, transportation, and even the manufacturing equipment that makes the food packaging and does the bottling and canning should be using food grade silicone lubricant.
The base silicone oil most commonly used in silicone greasing gel is polydimethylsiloxane (PDMS). It is clear, inert, non-toxic and non-flammable
After looking at the MSDS (Materials Safety and Data Sheets) of 8 different silicone lubricating grease products on the market, here is the gist of the risks with silicone paste:
- Hazards – None.
- First Aid – If swallowed, in eyes or on skin seek medical attention after immediately washing of area (mouth, eyes, skin).
- Fire Fighting – Non-flammable but will burn. Use water spray on fire.
- Accidental Release – Causes slippery surfaces that can become hazards.
- Safe Handling – No specific conditions.
- Exposure – Nil. Use safety goggles and gloves as directed by workplace.
- Toxicological – Non-irritant.
- Ecological – No specific conditions.
- Disposal – No special precautions. Follow local regulations.
- Transport – Nil conditions.
4. Why you should even bother to lubricate your pressure washer hose and wand o-rings?
It will make the o-ring last longer.
- Acts a surface surface film sealing the o-ring and metal surface as one.
- Protects the o-ring against cracking, pinching, cutting.
- Speeds up installation.
- Seats o-ring.
5. If you should use a spray can or silicone gel grease for application to rubber connections?
Avoid the spray can silicone lubricant varieties. The spray can will have petroleum based propellant and solvent to make it a spray. It will only be 5% (or so) silicone. Once the spray evaporates the silicone will remain. It is not as bad as a normal petroleum grease for rubber…
6. Best brands of silicone lubricant and where to buy online
There are 14,039 results when you search “silicone grease” on Amazon.com. There are 5,559 results for “silicone lubricant”.
How are you supposed to know which one to buy?
I’m glad you asked because we’re going to take a look right now. Since we established the spray can is not ideal, we have two options: do you want the grease or the oil?
Best Silicone Lubricating Grease
For all your silicone greasing needs, this tube by Danco will do the trick.
It is of course, as we have learned in the article, water resilient and great for use on rubber o-rings and seals.
On the packaging, you’ll notice it says ‘Keep Out of Reach of Children’ but don’t be alarmed this is just precautions so it not directly eaten or used as lip balm (or something similar). You can see the MSDS here.
Best Silicone Grease
DANCO Waterproof Silicone Faucet Grease
- Great for Plumbing
- Safe to Use
Best Silicone Lubricating Oil
What’s the point of the drip oil silicone lubricant?
The silicone drip oil is an option if you want to lube up a bunch of o-rings at once, and fast.
Put them all in a bag and dump some of the oil and shake the bag. Drip oil can also be used with an applicator brush or you can dip the part in a cup of the oil.
Pressure Washer Silicone Oil
3-IN-ONE – 120001 All-Temperature Silicone Drip Oil, 4 OZ
- Fast Drying
- No Mess
7. How often should you re-apply to pressure washer rubber o-rings (and proper technique)?
There is no 100% correct answer to this. You will hear different arguments from every person you ask. A safe bet is to apply new silicone grease in each of the below situations:
When changing o-rings
You will definitely want to use silicone lubricant when installing a new o-ring. It will ease installation and help seat the o-ring
Each time you reconnect pressure washer hose to wand and pump
Adding silicone grease before each use is overkill, in my opinion. However, I often leave my hose connected to wand and pump and reel it up for storage until next use. If I were to disconnect the hose each use exposing it to dust and shed environment, I would likely grease it before reconnecting.
Here’s a video by Parker Support on proper technique to lubricate an o-ring:
You can also see the difference between the grease and oil varieties of the lubricant.
- Silicone Grease. Wikipedia.org.
- Polydimethylsiloxane (PDMS). Wikipedia.org.
- OVERVIEW: Lubricants Why are there so many choices? www.JonEakes.com, November 21, 2015 .
- PDF: “What is the difference between Parafinic, Naphthenic, Hydrotreated and Synthetic oils?” www.lubegard.com. Web. 21 Apr. 2017.
- Wright, Jeremy. “Grease Basics.” Machinery Lubrication May 2008.
- Understanding the Differences in Base Oil Groups. MachineryLubrication.com. Web. 21 Apr. 2017.
- Choosing the Right Grease Thickening System. www.NyeLubricants.com. Web. 21 Apr. 2017.
- Global Automative Lubricants Market: Snapshot. www.TransparencyMarketResearch.com.
Jamey has been testing and reviewing top pressure washers for 7 years. He worked as a commercial pressure washer at a rendering plant for 3 years and all up has been using commercial and residential pressure washers for 15+ years. He is also a mechanical engineer and while working in the mining industry designed several turn-key light industrial vehicle wash pads.