Yong Heng air smells like oil

As long as you have the filters in place your ok, the air from all yong hengs is notoriously bad smelling no matter what, I use mine only for my older guns and scba tanks my big tanks “great whites” I have filled at a shop, I refuse to put that air in the big tanks, But with ghat said it has never hurt any tank or gun I use it in. All my fx’s and other higher end guns only get filled with clean dry air ,,
 
Purge the system of moisture, using the screw valves on both sides of the compressor, for a couple of seconds every five minutes while in use.

Change out your small YH filter every twenty minutes and set the old one out to dry and reuse later.

Add a better filter if needed to be sure more moisture and any oil smell is removed from the system. Many of us use this Tuxing three media filter although, if you feel the need, you can change media types at any time.

https://www.aliexpress.com/item/32891898253.html

A smaller one will probly do for some.

https://www.aliexpress.com/item/4000960926898.html?spm=a2g0s.9042311.0.0.2a034c4dL0nrJU

Possibly a filter similar to this if humidity is high in your area and your desiccant filters have to be replaced often.

https://www.ebay.com/itm/30MPa-High-Pressure-Air-Filter-Oil-Water-Separator-For-Air-Pump-Air-Tank/402600939671?hash=item5dbce2d097:g:pRoAAOSwy41f00pY
 
What oil are you using? Hydraulic fluid #46 smells the worst. Use a quality non detergent compressor oil like Secolube 500 from Filtertechs.com or Royal Purple. You can also remove the air smell from your tank by using a desiccant filter like the Tuxing gold filter with a desiccant bead/activated charcoal filter section in the filter cartridge. There are many threads on this forum on this topic.