quote:
Originally posted by Ray H:
Havoline Full Synthetic contains primarily Group III base oils. Group IIIs, like PAOs, are devoid of the aromatics (solvent-like compounds) that maintain seal condition in Group I and, to a much lesser degree in Group II, conventional motor oils. (Aromatics have ONE desirable attribute - maintaining mild seal swelling and pliability. Other than that, aromatics bring nothing remotely desirable to the table beause they're inherently unstable under heat and are subject to forming oxidation products - precursors to varnish and eventual sludge.) Consequently the synthetic base oils need seal conditioners to avoid oil leakage. Most often the seal conditioners used are select esters - generally carefully chosen to further enhance the finished oil's lubricity as well as providing controlled seal swelling and pliability characteristics.