Took my daughters 2006 Elantra in for a 7500 mile service. They changed the oil,rotated the tires ect. Picked it up and on the tag noticed they added bg oil additive with the change.Didn't charge me x-tra for it they just threw it in. Seems like they should ask, it isn,t their's. I,m not to much on additives, have no idea what this stuff is . If Ithink I need a better oil I'll go synthetic. Kind of ticked me off. Any opinions?