How to change the oil in my Speedaire compressor?

by meg
(Aldergrove, bc)

It's a 20 gallon speedaire model 3Z419J. I've lost the manual.

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Bill answers...

Hi Meg:

Every brand of compressor is slightly different, yet all reciprocating type compressors that are oil lubed have commonality.

So, the first question you need to answer is... is your compressor oil lubed for sure?

If you aren't sure, navigate to the Speedaire page on this website, find your local outlet using the guide provided, and ask them.

While you are at it, ask them if they can send you another manual too. :-)

All splash-lubed compressors have an oil sump somewhere under the compressor pump housing. They sometimes have a site glass too, to allow you to see how much oil is in the sump.

Run your compressor without oil and eventually it will seize, just like your car engine would if you ran it without oil.

Some compressors don't have a site glass, unfortunately, though some have a dip-stick built into the oil fill cap instead. Check yours for that as it will make refilling the oil to the correct level much easier.

Look for a plug near the bottom of the compressor pump housing that will thread out. That will be your oil drain. And yes, unless you are really careful, you will drip dirty oil all over everything. So pick your spot, one that won't be damaged by oil leaking onto it if you have a spill.

Drain the oil out into a reservoir that you can use to estimate about how much oil was in your sump. That way you can put the same amount back in, if you don't have a site glass or dip stick to measure the oil level as you refill the sump.


Near the top of the oil sump, usually below the piston housing, there will be a port into which you can add oil. I can't be more specific than that as there are so many brands of compressors, and many have quite different oil-adding ports.

The port into which you add the oil will be vented. That means that there will be a small hole in the cap somewhere to allow atmosphere into the oil sump as the oil is consumed.

Be careful! I'm not talking about the air intake at the top of the pump housing here. Don't put oil into that one.

After you have replaced the plug at the bottom of the sump, add compressor oil (not car oil, not 3 in 1 oil, only compressor oil) into the fill port until you've added about what you've removed. A little more will be OK, but very little more. You don't want to overfill the sump.

If you'd like to see some photos and step by step instructions for checking and adding your oil, pages 49 to 53 of my eBook The Home Compressor offer those. It's now $8.88, and is available right here.

Cheers,

Bill