Hello folks and how many of you folks here use either the QSGB and QSUD and like or dislike it? I have been using the QSGB 5W20 in a friends car for oil changes. No complaints from him. My father will NEVER use it or PYB for some reason, as he uses Valvoline. Anyways, I did some looking and cant believe the "stories and old wives tales" bout it causing sludge etc. Thanks in advance for the replies guys.