[Zeke]

As mentioned, air compressors are not the top item for the home shop anymore. The are handy and shouldn't overlooked as they do a lot more than run air tools.

Yes, I did say on the average that belt driven were more quiet than direct drive. California Air Compressors started a revolution and now there are more brands to choose from.

However, there are plenty of good used ones for sale and should be cheap. Used tools are not selling well with some exceptions. I don't want to go on record as making a statement that might ultimately be wrong because there are always exceptions to any rule. But oil filled compressors tend to send oil into the tank and that is why we use water traps and filters when needed.

Since this is generally accepted, the inside of most tanks is oily, not rusty. You can tap an empty tank and listen for dead spots on the bottom. You can take the fittings out of the air outlet bung and look inside and even listen as you roll the tank or tip it up where the hole is at the bottom. If you detect rust flakes, pass. If the outside is rusty as in scale rust, it's trash.

I don't recommend removing the larger hole threaded inspection plugs as they are nearly impossible to remove and hard to reseal. If in doubt, don't buy it.