sxg6: Perhaps someone can explain to us how a TBN of 5.0 can meet ACEA A3, ACEA B3 which is a stable, stay in grade, oil intended for use in high performance engines and/or extended drain intervals where specified by manufacturers,... I noticed on Castrol USA today that most of Castrol Syntecs meet those specifications, including the 10W-40 that I was researching. Perhaps it's a matter of its TBN being much more stable to begin with. I'll watch for what some of the real knowing ones come up with on this.