This fuel sample was taken from a VW Jetta that was brought in for a poor running condition. Diagnostics determined the probable cause was fuel contamination, seen in this sample collected. The fuel filter was stopped up from the contaminants you see, causing random engine misfires due to inadequate fuel flow/volume. We recommend changing your fuel filter every 30,000 miles or so (if serviceable) and using high quality gasoline (a.k.a. top tier, name-brand fuel) to keep your fuel system clean and happy.
Video provided by Forest Automotive: Complete Auto Service & Repair in Lynchburg & Forest, VA.