<p>Multi-tasking is great. Anybody with the ability to do a few things at the same time (like pretty much every mother on the planet) and do them well has been truly blessed. What&#39;s true with parenting and circus clowns doesn&#39;t hold when it comes to your car&#39;s systems. This reader&#39;s air filter has turned to multi-tasking, only it&#39;s not a welcome change.</p><blockquote>Dear Matthew, Thanks for providing so much useful information on the site. I have been able to try and successfully pull off automotive feats I thought were out of my league by a long shot! Recently while doing my regular maintenance I went to <a href="https://www.thoughtco.com/kandn-million-mile-air-filter-review-533699" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="1">change my air filter</a> and found that it had what appears to be motor oil splashed on it. The car is a 1991 VW Jetta, manual transmission with 148,000 miles. I know it couldn&#39;t possibly be oil from my engine. Is it possible that some black fluid was splashed into my engine from the road? I can&#39;t figure out what to do, or if I need to do anything at all. Please help, Travis</blockquote>Travis, congrats on almost reaching the 150k mark with your Jetta. You must take pretty good care of it. As for the oil on your air filter, no it probably didn&#39;t splash up from the road and it is oil from your engine. How did it make it all the way to your air filter? The PCV valve. If your PCV valve goes bad, the entire system can back up, spit up and screw up. So far yours has backed and spit but you caught it quick enough to avoid the screw. <a href="https://www.thoughtco.com/how-to-replace-a-pcv-valve-281743" data-component="link" data-source="inlineLink" data-type="internalLink" data-ordinal="2">Replace your PCV valve</a> and your air filter will be pristine once again.