of course the first # is COLD flow @ 40C the second @100C, + agreeing with you a thicker oil film from a higher viscosity will protect better IMO. most 5W's-XX are similar at startup although different-better base oils aka real synthetic PAO + Esters thicken LESS as temps drop under the spec @ 40C, on that same note real synthetics thin less after 100C spec as noted on machinery lubrications curve cited in a past article. only those in EXTREME temps really benefit or need the costlier TRUE synthetic lubes. wishing everyone a HEALTHY + happy holiday!!! DONT eat + or drink TOO much!!!!!