So, how bad is unfiltered air?

[DaV8or]

Two issues. I have the cowling completely off right now and I'd like to clean and run the engine on the ground to track down my pesky oil leak/s. This would mean unfiltered air on the ground without the lower cowl. Bad idea? Second issue involves the ram air boot. the one I have looks to have been repaired because it has what appears to be silicon/RTV type caulk on one side of it. It seems to be holding up just fine and there are no leaks that I can tell. Should I put a new one in right away for about $300 since it is easy to do now, wait until annual, or just wait until it actually fails? How bad is unfiltered air really?

[sleepingsquirrel]

You might sweep the area in front of the airplane to see what you can keep from becoming airborne and sucked into the intake.

A simple experiment would be to clean the filter or put a new one on. I doubt you would find anything of any consequence for two or three hours of running if you closely inspected the filter by weighing it before running then after. These filters are really just keeping the June bugs out, just look behind the filter at the debris that makes it through.