Type of oil to use in compressor?

I own a yong heng and manual says to use hydraulic oil 46. I found 5 gallon bucket for about $30. But I seen people say dont use hydraulic oil. They said to use the royal purple. I found 1 gallon for $75. Wth...$75 for 1 gallon?? Really? So to get 5 gallon of royal purple is $375. Smh. The other which the manufacturers recommend is $30 for 5 gallons. Which oil to get? Is it really worth over 10 times the cost to get royal purple? Or it doesnt matter which oil I get.

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I started with #46 hydraulic oil. Then I heard that it's no good and "real" compressor oil should be used so I did and switched to #100 compressor oil. Both are cheap stuff from China costing 3 bucks per liter. Could not see any difference in the rate of the oil turning dark. After 8 hours of run time, there is not any significant wearing on the con rod bearing which is plain aluminum rubbing on steel. If this part has not worn out, the other parts should be in good shape. Now I am doubting whether the choice of oil is really as critical as some have claimed for compressors of this kind. If I were to select an oil, I will look for one that will prevent thick oil dirt from building up at internal reed valves as this can cause pressure build up failure. This has not happened on my Yong Heng yet but I did have experienced mild internal leakage which was fixed by cleaning the reed valve blades. I am planning to stick to the oil that's being used now and see what will happen as time goes by. The worst thing that can occur is breaking down of parts but all can be replaced easily at very low cost so there is really nothing to worry about.

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I am currently using RP. I have 6 hours on my Yong Heng. I changed the oil after the first 15 min run and did not find any particles in the oil. I then changed it again at 3 hours. Absolutely no sign of the oil degrading. Next oil change will be at around 7 hours. A quart is good for 3 oil changes / 12+ hours of run time (on my schedule). At that rate the price of the oil is not an issue for me and I don't need to buy it by the gallon. I also like the squeeze bottle with spout that the RP comes in. Makes getting the oil in the Yong Heng easy - no mess and precise control when filling.
 
If you were to have bought an expensive high end compressor for business shop use then you might consider getting an expensive high-end oil as well. However, with these inexpensive, sloppily built and mass-produced compressors, anything synthetic made for compressor work will do, regardless of the name brand. Like most oil's, it is likely made in the same refining factory and the bottle labeled according to the current buyer's name. Off brand oil bottled for your car is done exactly the same way for the most part, depending on the manufacturer on the bottle. In other words, you may be paying $2.00 a quart for Valvoline manufactured/produced oil bit with an Ace Hardware label on the bottle. The MSDS sheet tells who bottles it. Whichever oil you choose, change it often, as it is cheap insurance to engine longevity.
 
Hello! I have a 2017mfg. dated Yong Heng on the way....Like most concerned consumers who do not want to experience mechanical failure and down time I have been extensively reading my face off on the topic of which oil to use.......of course.😒 So it seems to me that airgunners are having positive results with both schools of practice......The #46 and the Royal Purple...

As I read through these posts in this thread it seems (correct me if I'm wrong) that there is different classifications or grades if you will of hydraulic oil? So we have the two popular ones #49......#100 (as on the Royal Purple label) which I personally have not thought to dive into the differences yet.....😴 Yet......So, as I think about this topic of which oil to run with, doesn't it all come down to the metals involved, amount of heat/load, clearances (needed viscosity), and bearing surfaces.......Right?? Is hydrolic oil different than compressor oil? Labeling and wording on product can be tricky at times......👀

We need to collectively come to a fact-based conclusion so this issue can be put to rest.....I also don't like to spend unnecessary money, yet if I go the cheap route on something and experience premature wear and or failure......It would have then behoved me to spend a few extra dollars.....Right??

What's the LONGEST an avid/frequent user of their YH has had solid, reliable performance and what oil have they had in their unit??