After constantly getting fed up with my 24l (Oil Free) compressor
running out of air, I have upgraded to a 100L model. But this one needs
The oil level is a little low in the window and I would like to top it
up, so what oil do I use? Can I use standard 4-stroke motor oil, or do
I need something special?
What about mixing? If I don't know whats already in there, is it 'safe'
to just top it up or should I drain it first?
Any info would be appreciated
Interesting.. I will see what I can find in the UK.. It appears that
they are all synthetic, and rather than take the risk of 'mixing' oils,
I am tempted to drain mine and add all new oil
Many thanks for the info
Is it a standard piston compressor with a splash-lube crankcase, or
pressure lube? Who made it? Model number? How many stages and how
If you can't find a data plate and don't know who made it, put
pictures of the unit up on a webpage somewhere and point us to them
with a link here. Someone (probably in the European contingent) will
recognize the maker, and can give you clues as to where to get the
definitive maintenance information.
You usually use a non-detergent oil in an air compressor, and the
additive package is significantly different from regular gasoline
(petrol) or diesel engine oils - but they will work. Some makers
specify a synthetic lubricant in their two-stage units because they
run very hot at maximum pressure.
Do NOT mix new and old oils if you have no idea what's in there now
- even if it's a bit low there is oil in there. The odds are very low
IMHO, but if they've got some odd oil in there you could have a
reaction in the crankcase between the new and old oils, and gelled
goop doesn't lubricate the bearings at all.
If it's a screw compressor (Roots Blower - usually 25 HP or better)
they require a totally different type of lubricant, and instead of a
regular air receiver they have a pressurized oil separation and
lubricant supply tank in the air output that recirculates the oil.
The compressor is made by 'Valley', buts its just a cheap, rebadged
generic compressor made in China..
Its an upright, 3hp, single piston type with a very similar 'engine' to
my old Oil Free 24L version (again, a cheap, rebadged import).
I think that I will drain the old oil out and put in some new stuff...
I found in the (limited) instructions that it suggest N32 oil in the
winter and N68 in the summer.. I guess this "ISO" number.
One questions about oil changes is, how do I get all of the old oil
out? Obviously I heat it up, open the drain plug and tip it out, but do
I have to get EVERY drop out? Does it matter if there is still a little
bit left over?
I think I know where I can get the right oil in the UK, so am going to
change whats in there, just in case.
All the best
If you are worried about reaction between existing oil and new oil
then you will have to empty, then flush with new then empty several
times to be sure none of the old oil is left behind.
As it is a generic Chinese machine I would just go to your local
Machinemart and buy a bottle of their compressor oil and top it up.
Yes - sounds like regular SAE20 - ISO68 non-detergent petroleum
based will do just fine. It isn't one of the fancy types. And if you
don't operate it regularly in sub-freezing cold areas, you don't need
to worry about putting ISO32 "winter oil" in.
Do not worry about that - I mentioned it on the off chance this unit
was something exotic bought as surplus that used an exotic oil.
When you do the first oil change (after you wipe up the mess as the
oil flows down the side of the unit...) is the time to add a pipe
nipple and any elbows needed to get the oil drain to a convenient spot
for the catch bucket. Make future oil changes neater.
But if you put a ball valve in the oil drain line, be sure to put
the pipe plug back in the end, too - there are gremlins that turn
valve handles. (2-year olds, cats, piles of junk falling over...)
It's like a car engine - they want you to run it for an hour
unloaded (with the air output line unplugged, no pressure in the tank)
for ring seating, then you change the oil after 5 to 10 hours to get
rid of the initial manufacturing sporge in the compressor crankcase,
then every 50 hours.
Do you have an hourmeter wired across the motor yet? Cheap way to
remind yourself to change the compressor oil once in a while.
Compressor oils are BS. I bought a 2 stage 5 HP cast iron compressor
new in 1975. Let me say it runs over 5 hrs a day (due to my CNC
machines needing so much air). Every 3-4 years I have to change the
valve plate. When I do the hone marks are still on the cylinders.
What oil do I use 10-30 motor oil, same as you put in your car.
I change it once a yr & at 5 hrs running 6 days a week that's a lot of
use. So it's now 30 yrs old & still running fine.
The only problemis that Machinemart only do SAE40, which is ISO100 in 1
litre sizes.. If I want 30 (ISO68), I have to get 5litres which may be
a bit of an overkil.
I have found another place which does 30 in 1 litres bottles, so will
get some of that.
Still a little concerned as to whether I should just 'top it up' or go
a complete change!!
Why do I worry about everything? :)