essentially I guess that's what I'm starting to question myself (just now, thinking aloud on this board I guess). I've always been told, recommended, etc. that synthetic was better for the vehicle. But for some reason I keep running regular in the wife's car (I guess because it's so clean all the time). So yeah, one would think they would recommend it in the owner's manual if it really was better. I'm starting to wonder if just running regular and changing it more frequently would be the way to go. It would also be less expensive that's for sure!