A while back we discussed grease used in GX compressors, especially the gear drive. As you may know, I open my compressors fairly often to keep track of the wear and grease migration, and I have begun a trial lube regime.
1) Let's tackle the gear box first. The factory grease is SUPER sticky and thick. Upon opening my compressor in the last few months, I've kept track of what the gears looked like and where the grease migrated to. It was worrisome that every time I opened the gear box the grease was stuck to the walls more than the gears, leaving large sections of the larger gear dry or nearly dry. As long as a good portion is lubed, it will distribute during running. The last time I opened it, (today), it was largely dry, which led me to do some research and make some changes. I cleaned out the old grease in the gear box as best I could without removing the large gear. Using alcohol, screwdrivers and lots of paper towels and elbow grease, it came out largely clean. Research followed looking for an acceptable grease for this gear drive. There are many good choices, and for the moment I chose what was handy. You could use cornhead grease, or any NLGI 00 grease would be very good. 00 grease is thin, almost like honey, and would stay in the bottom of the gear box, being distributed during running. You might have to use some RTV on the gearbox to keep the grease in, but on mine it doesn't leak. I put Shaeffer's 279 moly NLGI 00 grease in mine as a test run for a few weeks for now. I also believe that 00 might just be a bit thin, so I ordered a tub of Renewal Lubricants Food Grade EP NLGI 0 to try next. This is a recommended gear grease, and the NLGI 2 version is what I use in the air side of the compressor, so one grease for everything. I don't see the need for moly in any of the parts of the compressor. In fact you could make the argument that moly is contraindicated for the connecting rod roller bearings.
So, for now, I'll use the Schaeffer's 00 moly.
2) For the air side, piston, rod, etc. I cleaned everything very well. The moly grease used on the wrist pin has been migrating all over the piston and cylinder. So, I decided to use RL #2 on everything. There is nothing here that would indicate that this is not a great choice for this application. Also, it seems the way the moly had migrated into the cylinder, would be a fantastic way to lightly lube the piston, cylinder and seals.
To conclude, one grease, two consistencies [Renewal Lubricants Food Grade EP NLGI #0 and #2] for the entire compressor. I do believe the failures that we've seen in these units involving the gearbox is caused by the grease used at manufacture. It makes sense, that it could conceivably last 3 years or so, and it definitely would not migrate out of the gearbox during shipping, so that's likely why they chose it. It is about an hour's work to clean out the grease in the gearbox, but it is time well spent in my book. You could use all kinds of fancy greases, but there's just nothing here to indicate going crazy. For the gearbox, there are two avenues of thinking. One is a super tacky grease to adhere to the gears, and it certainly would work but it also will eventually migrate off the gears with use. It takes time, but it happens. The other is a thinner gearbox grease, that will flow back to the bottom of the gearbox and any time the compressor runs, it will distribute itself all over the gears. To me this is a much better long term solution, but it is obvious that the compressor could not be shipped this way as leakage would be almost guaranteed.
1) Let's tackle the gear box first. The factory grease is SUPER sticky and thick. Upon opening my compressor in the last few months, I've kept track of what the gears looked like and where the grease migrated to. It was worrisome that every time I opened the gear box the grease was stuck to the walls more than the gears, leaving large sections of the larger gear dry or nearly dry. As long as a good portion is lubed, it will distribute during running. The last time I opened it, (today), it was largely dry, which led me to do some research and make some changes. I cleaned out the old grease in the gear box as best I could without removing the large gear. Using alcohol, screwdrivers and lots of paper towels and elbow grease, it came out largely clean. Research followed looking for an acceptable grease for this gear drive. There are many good choices, and for the moment I chose what was handy. You could use cornhead grease, or any NLGI 00 grease would be very good. 00 grease is thin, almost like honey, and would stay in the bottom of the gear box, being distributed during running. You might have to use some RTV on the gearbox to keep the grease in, but on mine it doesn't leak. I put Shaeffer's 279 moly NLGI 00 grease in mine as a test run for a few weeks for now. I also believe that 00 might just be a bit thin, so I ordered a tub of Renewal Lubricants Food Grade EP NLGI 0 to try next. This is a recommended gear grease, and the NLGI 2 version is what I use in the air side of the compressor, so one grease for everything. I don't see the need for moly in any of the parts of the compressor. In fact you could make the argument that moly is contraindicated for the connecting rod roller bearings.
So, for now, I'll use the Schaeffer's 00 moly.
2) For the air side, piston, rod, etc. I cleaned everything very well. The moly grease used on the wrist pin has been migrating all over the piston and cylinder. So, I decided to use RL #2 on everything. There is nothing here that would indicate that this is not a great choice for this application. Also, it seems the way the moly had migrated into the cylinder, would be a fantastic way to lightly lube the piston, cylinder and seals.
To conclude, one grease, two consistencies [Renewal Lubricants Food Grade EP NLGI #0 and #2] for the entire compressor. I do believe the failures that we've seen in these units involving the gearbox is caused by the grease used at manufacture. It makes sense, that it could conceivably last 3 years or so, and it definitely would not migrate out of the gearbox during shipping, so that's likely why they chose it. It is about an hour's work to clean out the grease in the gearbox, but it is time well spent in my book. You could use all kinds of fancy greases, but there's just nothing here to indicate going crazy. For the gearbox, there are two avenues of thinking. One is a super tacky grease to adhere to the gears, and it certainly would work but it also will eventually migrate off the gears with use. It takes time, but it happens. The other is a thinner gearbox grease, that will flow back to the bottom of the gearbox and any time the compressor runs, it will distribute itself all over the gears. To me this is a much better long term solution, but it is obvious that the compressor could not be shipped this way as leakage would be almost guaranteed.
