Is anybody using Castrol Synthetic Blend? I am currently using Royal Purple and kind of tired of having to add oil every 3K. Getting pricey. I am not trying to be cheap but want to find the best oil at the best price. I mean, I was missing nearly two quarts of oil last time I changed (around 5K miles) using Royal Purple. Would rather use SynBlend b/c it is cheaper if I am going to have to add more often than originally suspected. Also, only 22K on motor.