The air cleaner cover that pops off to allow the changing of the pleated air filter also has what appears to be a mesh-type filter that the air must also pass through before it enters the air intake throttle pipe. Is this second filter really a filter or does it have another purpose? What maintenance is needed for this? Should it be cleaned periodically and maybe coated with a fine film of oil? I did not see anything about it in my owners manual or in the repair manual (Volume 2- Diagnostics, Engine, and Hybrid Components) that I just received (cost about $110).