i was at my walmart earlier, and have doen this before. okay i know this soudns funny, strange stupid, lol, but think about it! i shook supertech 5w30, seemd kinda hefty actually.. then their 10W 30, the 10W30 seemed much lighter than the 5w 30! then i shook thier 10W 30 high mileage, and it was THICK! i shook mobile clean 5w 30 and it was VERY thin. think in doing os, per bottle can give you an idea, about the possible CCS or how thin/whick it will be when hot? or at start up? thinnest oils ive found, were castrol easy start up, mobile clean 5,000, and valvolines durablend.