A method 1, wherein {HEAD ~ the engine oil} has {TAIL ~ at least 6% mass}, soot loading 
has
A method 1 , wherein { HEAD ~ the engine oil } has { TAIL ~ at least 6 % mass } , soot loading
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH