So many oils, so little time. In Mal-Wart this AM and found Supertech "full synthetic" 10W-30 for $11.48 in the gallon jug, Rotella Synthetic 5W-40 for $12.35 in the gallon jug, and Castrol Syntec Blend 10W-30 for $12.48 in the 5 quart jug. Which would you choose for an upcoming 5K OCI in a Volvo 944 turbo (wifemobile, 99% city driving, Florida heat, not driven hard, consumes about 1 qt/2,500 miles)?