Question on oil-type air compressors


Hello,
I've recently acquired a second hand oil-type cast iron belt driven compressor. Is it normal for there to be some oil in the water drained from the tank? Also, the oil site glass has no markings on it--should the oil level be half-way up, all the way up, or what?
Thanks, Wayne
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Wayne Whitney wrote:

yes, it is common for piston-type compressors to pass a little oil. I believe the oil should be to the bottom of the sight glass but check your owner's manual to be sure. If you don't have one I bet you could find a .pdf online. I'd change the oil anyway, it requires the same sort of maintenance as your car would (as it is a very similar mechanism.)
good luck,
nate
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Some oil in the air is normal. Worn piston rings, wrong or too much oil in the crankcase, or oil needing changed can increase the amount. Don't worry about it unless you have trouble keeping the crankcase level up.
The correct level for most sight glasses is half-way. A straight 30W non-detergent oil is usually satisfactory if you can not find the manufacturers recommendations.
Don Young
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Most compressors will pass some oil. If there is a lot, it means the compressor is wearing out. Most air systems have some sort of filtering system on them. Commercial and industrial systems can have rather elaborate dryers, oil separators, etc. If you plan to spray paint, look into a filtering system. Keep the tank drained as well.
If you keep the oil level visible in the sight glass you are good to go. Don't overfill it either.
Some of the old cast iron compressors just keep on running for years. They are quiet compared to most of the oilless models too.
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OK, as you mention for spraying paint, this oil needs to be filtered out. What about for air tools? Is the compressor oil comparable to the air tool oil, so its presence in the air stream is a benefit?
Thanks, Wayne
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If the oil is reaching\\the tools, so is some of the water carried with it canceling any benefits of the oil. You end up with gummed tools. Clean air is always best.
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