I honestly thought it would be a gimmick, but I filled my car with a "generic" brand instead my usual brand, and my fuel economy went down and there was a noticeable vibration when idle, so I went back to Shell. I have always had really good luck with Shell in all of German engines.
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BMW History:
2000 328iS|2002 E39 530i|2005 E60 530i|2007 328i Coupe|2009 335i Coupe|2012 335i Coupe
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