Originally Posted By: addyguy
Esters.
I had the opportunity to talk with a chemist from XOM.
He told me that all GP II/II+ oils required some esters for seal conditioning. GP III oils required esters also, more-so than the GP II oils. GP IV oils required the most esters for seal conditioners. That is whether they are high mileage or regular oils.
I can't get a "yes"/"no" answer from XOM, or anyone else, if their HM oils actually use "MORE" of these esters or if they just advertise them more seriously.
I do know that Valvoline, in their MaxLife and MaxLife synthetic,(their HM oils) do use a heavier base oil(higher HTHS), higher 100C cSt, more anti wear, more friction modifiers, more antioxidants. They also advertise and warrant that the "seal conditioners" they use are compatible with factory new and rebuilt engines.
Mobil 1 HM oils have a heavier base oil(11.79, 3.66 HTHS, for 10W-30 HM) vs (10.0, 3.14 HTHS for their regular 10W-30) more ZDDP, 1000 ppm, more moly, more boron, more detergents, and more antioxidants. They also advertise their seal conditioners.
I, personally, do not use 30 grade oils, but, if I were to use one, it would be either Maxlife 10W-30 full synthetic, Mobil 1 10W-30 HM, or Amsoil 10W-30 XLT. I know that XLT is not a HM oil, but look at that add pack, HTHS, and TBN.