I recently went with Mobil's Super 5w30 High Mileage because I have leaky valve stem seals in a 2001 Taurus (29k mi on the odo). It stated "seal conditioners" on the back.
The odd thing about this new Mobil is that despite it being a High Mileage oil, it still meets API SN + Resource Conserving unlike (almost?) all other High Mileage oils that are at the thicker end of their SAE grade.
The spec sheets tell a very strange tale regarding this High Mileage oil.
Super 5w30 vs. Super High Mileage 5w30
.......
Pour Point = -36 vs -36
Flash Point = 221 vs 222
VI = 158 vs 159
CCS,cp = 6,080@-30°C vs 6,000@-30ºC
MRV,cp = 26,800@-35ºC vs 26,400@-35ºC
cSt at 40°C = 63.95 vs 61.14
cSt at 100°C = 10.7 vs 10.4
Compare this to for example Valvoline 5w30
Conventional vs High Mileage
.......
cSt at 40°C = 63.0 vs 67
cSt at 100°C = 10.78 vs 11.5
