I have AGONIZED over thsi exact same thing.
IN THE BLUE CORNER: Mobil 1 -FULL SYNTHETIC- High Mileage.. Oooo. Aaaaah.
WALMART: $23 for 5 QUARTS...
POINTS FOR: Name and Reputation.
API SERVICE: SL.
IN THE RED CORNER! Valvoline MaxLife -FULL SYNTHETIC!!!-
WALMART: $22 for 5 Quarts ($15 for Blend, but Full Synthetic is alluring to me.. cant go werong, and why not.)
POINTS FOR: Name, Reptation.. AND Additive Pack of MaxLife, HIGHLY acclaimed.. AND ORIGINAL High Mileage Oil in BLEND!!
API SERVICE: -SM-
Based on this.. I choose MaxLife. Particularly if yo uhave been using MaxLife SB already.
This i have thought, over, and over, and Over...
I would be more suspicious of M1, as it seems to be more "High Performance" (Corvette, Porsche, etc) and less "High Mileage" Reputation.
Oh, and PS: They had Full Synthetic in 5W-30.. M1 HM in only 10W-30 and 10W-40. V ML FS in all three grades.