Haven't seen a good discussion between these two brands. I knowQuaker State Ultimate Durability has a loyal following but Valvoline has a good product as well. I've used SynPower with good results, so this would be my first time usingQuaker State Ultimate Durability (on sale). Should I pay the extra for SynPower or save a few $$ onQuaker State Ultimate Durability? Not sure if the difference is really significant, so I'm leaning towards the cost savings with Quaker State Ultimate Durability. Forum thoughts...