We have a couple of old Lexmark 2500+ series dot-matrix printers still in service that are used to produced shipping labels, one or two or ten at a time. These printers have a horizontal metal shaft and the printhead slides back and forth on that shaft, driven by a motor and cogged belt. One of these printers has started to malfunction and as best I can tell it's because the printhead/shaft mechanism is in need of some lubrication. If you slide the printhead manually, you can feel resistance. Cleaning the shaft with rubbing alcohol seems to provide a temporary fix. Once upon a time, I was told that printers of this type should never be oiled as it would ruin the bearings in the printhead mechanism. However, according to the service manual on this Lexmark this one should be lubricated when certain parts are replaced, including the "oil felt (carrier block)". It further goes on to say that only mineral oil based lubricants should be used and gives a Lexmark part number 1280443 and these approved equivalents: Mobil DTE27, Shell Tellus 100, Fuchs Renolin MR30. My questions are, should I be lubricating this printer even though I'm not replacing any parts? Secondly, I'm having difficulty finding the specified lubricants in any size other than 5 gallon containers, costing over $100 each. These all appear to be "anti-wear hydraulic oils". Am I obsessing too much trying to find the exact spec oil or can I get by with something off the shelf, as long as it's mineral oil?
Best to use what the manufacturer says, but you don't need gallons of it.
"oil felt (carrier block)" <--- This is probably what you need to oil so it can oil the shaft.
Mineral oil is OK, or machine oil (hardware stores have this) but never vegetable oil compounds.