If you have an oil-lubricated air compressor, the owner’s manual will tell you to use compressor oil, not motor oil. But, does it REALLY matter? It turns out it does - we’ll tell you why in this episode!
The manufacturer of your oil-lubricated air compressor tells you that you must use compressor oil specifically to lubricate your unit’s air pump. Is this just a strategy to sell another product and one that is more expensive at that?
Nope, there are legitimate reasons to use the specified compressor oil. While it’s true that both combustion engines and compressor pumps generate high levels of heat, the source of that heat is different. Heat in the combustion engine comes from combusting fuel. Heat from a compressor pump comes from pressurizing air and to some degree (pun intended), friction.
Compressor oil is formulated specifically to have the correct viscosity to keep operating surfaces inside the pump lubricated, even during start-up and immediately after beginning operation. Besides that, pressure builds up inside the pump significantly more than the “lower half” of a combustion engine, so the oil needs to stay fluid and in place, even under high pressures. Compressor oil does that very well and greatly reduces wear and tear on the compressor pump’s moving parts.
Compressor oil is almost always non-detergent. Detergents are added to regular motor oil to keep soot (a by-product of combustion) in suspension, as well as other impurities, including water. Some detergent additives also help control the acidity that forms in the base oil. Acid inside a combustion engine is not a good thing! Why wouldn’t detergent be a good thing in a compressor pump? Detergent also can more readily lead to emulsification of the oil - when oil and water are blended by continual agitation - much like oil and vinegar in your favorite Italian salad dressing. That’s great in a salad, but not in a compressor pump. Because the water and oil won’t readily mix in the absence of detergent, the water settles out in the base of the oil sump (water is heavier than oil, oil “floats” to the top as seen in oil-slicks) and is easily drained off during an oil change.
Keeping small particles in suspension isn’t good either inside an air pump. It’s better if they separate out instead of clogging up minute passages in the pump and components.
Most small to moderate-sized compressors have their pumps cooled by air - but that’s only part of the cooling system. The oil itself is a component of the cooling system. Compressor oil is formulated to provide efficient cooling and heat dissipation. This helps maintain the best operating temperatures - thereby prolonging the life of the compressor.
With compressor pump oil being changed out at the recommended service intervals, and the break-in oil in a new compressor pump being changed after about 20 hours of operation, you can expect many years of service from your unit’s compressor pump.
While you could use regular motor oil in your compressor pump, and you wouldn’t see immediate side effects, why do that? You’ve got an investment in your compressor, so take care of it by using the specified lubricant and get a longer-term return on your investment. It’s a wise decision. Oilless air compressors are becoming more available and are increasingly popular. But, what are the trade-offs between oiled and oil-less compressors? Check out this episode where we demystify the two types and give you the information for you to make your own decision:
We’ve installed a moderately sized single-stage compressor in our shop, that utilizes an oiled compressor and large cooling fan. It’s the DeWalt® DXCM303. We think it’s a great compressor for the price and fits well in a small to medium-sized shop environment. You can check out our product overview here:
When we’ve had the DeWalt®DXCM303 Single-Stage Compressor in service for over a year, check out our review on how it held up and is performing here:
COMING AFTER ONE YEAR OR MORE OF OPERATION!!!
We like the DeWalt® DXCM303 Single-Stage Compressor, but some after-market enhancements make it easier to service and run better. Check out our “Pimp My Compressor” episode here:
COMING SOON!
Hey, Dirt Farmer Jay here from DirtFarmerJay.com.
Well, you've got yourself an air compressor that uses oil to lubricate the air pump.
Well, do you have to use what the manufacturers recommend?
That's full synthetic, non-detergent air compressor oil.
Or can you use just regular motor oil?
What's the difference?
Stick with me and I'll tell you all about it.
Hey, Dirt Farmer Jay here from DirtFarmerJay.com.
Recently, we upgraded our oiless air compressor to an oil lubricated compressor.
And we'll tell you all about that in another episode, how we like it.
So far, we're loving it.
But one of the things that came to mind right away is,
do you really have to use this kind of dedicated
non-detergent air compressor oil with these kinds of compressors?
Or will a good motor oil work just as well?
Well, as it turns out, it really does matter.
It's not just a gimmick by the manufacturers to sell you more expensive oil.
And this is more expensive.
This is November of 2023.
This runs about $14 or $15
for 16 fluid ounces or 473 milliliters.
And you know, you can get a quart of good synthetic oil
with moderate viscosity.
This one here, for instance, this viscosity is 5.30
for a broad range of operating conditions.
You can get it a lot cheaper than nearly 14 or 15 bucks per 16 ounces.
So why the price difference and why is this important?
Well, it turns out for a couple of reasons.
Number one, the viscosity of these are right for the operating conditions
in an air pump.
It keeps things lubricated during the initial startup.
And this is especially important if that compressor is being used
in cold conditions.
You've got out in a garage or an unheated shop
that needs to be warmed during the time you're working in it.
But one of the first things you turn on is your compressor.
And if the compressor is really cold,
you've got to make sure the oil's in place and all the lubricated surfaces
or the areas that need lubrication from the get go.
So right viscosity is the first reason that you would want to make
this your choice for your compressor.
Number two, this is a non-detergent oil
versus most of motor oils are now detergent.
And you go, well, why does that matter?
Because I would think detergent would actually help keep things cleaner.
And it's not actually just laundry detergent or something like that.
It's an agent that keeps things in suspension.
So a little bit of a difference between the two types of
of operating conditions on a combustion engine
that this type of motor oil is used for.
Ignition occurs on the top half of the engine,
that is on the top surfaces of the piston.
And there's a little bit of residual of the fuel
burn off of carbon that builds up.
And so that carbon ends up in the lower half past the rings of the piston
through normal operating of the engine.
And that's why you'll see as oil ages while it turns dark.
It's usually carbon buildups.
Well, what the detergent is doing is keeping it in suspension
so it doesn't build up in any area of the engine.
And you get a large piece of carbon buildup.
And then all of a sudden it lets go,
clog somewhere in the engine, an oil galley or elsewhere and causes problems.
So detergent oil is there.
Now, in an air compressor pump,
the compression is driven the other way around,
whereas pistons are driven up and down
from the top with ignition in a fuel driven engine.
When you're using an oil pump and a compressor, it's the other way around.
There is a pulley with a fan that is driving the crankshaft backwards.
And what's happening when I say backwards,
I mean differently than the other type of engine.
And what's happening is the compressed air
is produced by intake on one half of the head ceiling off.
And as the piston rises, it presses the air out into the compressor tank.
So there is no combustion happening.
Therefore, you don't end up with a lot of carbon.
But something else happens in an oil pump
where you are using it for your compressor.
And that is when you take moist air, even that has a little bit of humidity in it
and you compress it, it's going to squeeze the water out of it.
Well, where does that water go?
Three places. One, back into the oil crank case
and around the pistons itself in the pump.
Number two is into the tank itself, the storage tank.
And number three is in the air that's blown out.
So that water, if it gets to be a significant amount,
really causes problem in all three areas, rusting out a tank,
fouling up paint finishes or messing up tools.
But in the oil pump, it can lead to rust.
And if there's water that is being kept in suspension
because of the detergent type of oil,
then that water is coating the inside.
And water is not nearly as good a lubricant as this oil is.
So you don't want that oil to have water in suspension.
That is called emulsification.
And if you're thinking, I'm not familiar with emulsification,
that's where you get oil and water to mix together.
But I bet you are familiar with emulsification.
Let me show you.
If you've ever enjoyed.
No, this is not an ad for Olive Garden Italian dressing.
But if you've ever enjoyed good Italian dressing or made your own,
you're familiar with emulsification.
That's where you try to get oily substances to mix with water based substances.
The only way you can keep the two in suspension together
like it is in this commercial product is to use some kind of agent
that stops the two from separating out from each other.
But if you've done some of your own type of salad dressings that use oil and vinegar,
you know darn well they separate out and you have to shake them vigorously
to beat them together to get them to blend.
Well, in a similar way, that's what's happening inside the oil pump
where you have water that is now in the oil
and it's being beat by the crankshaft,
the connecting rods, all that to the pistons.
And if that water is not separating out, it'll now emulsify the oil.
And you can tell it by the oil turning really milky white.
So what happens when you're using this?
The water drops to the bottom of the sump
and is drained off in the next change, along with little minute particles
of worn metal as the engine or the pump polishes itself through operation.
So this is key for correct operation.
If you'd like to see our experience and our thoughts
on that new DEWALT DXC M303 compressor we bought,
check out the video right there and you'll just kind of get a walk
through of some of the key features and our initial impressions.
And while you're at it, check out this other video that YouTube
thinks is perfect for you.
And we'd love it if you'd watch it, too.
Until the next time.
This is Dirt Farmer Jay taking care of business with that new air compressor.
