Just went to JL to get an inspection and oil change on my '03 Tahoe. Cat was the cute young lady tech that was assigned to me. First, she told me that my car's manufacturer recommended a synthetic blend. Really? Then she told me that if I had synthetic oil or a blend and went to conventional oil that it could damage my engine. Really?!? Last but not least, she showed me the JL spec sheet for the Tahoe and said "See, right here it calls for SAE 5W30. That's a synthetic blend." BAHAHAHAHA!!!!!