I have to abide by the 5k oil change under my warenty. VW reccomends a 5w-40 for my v6, which means a synthic, I guess, because I haven't seen a dino 5w-40. I don't want an oil that will shear and cause sludge, but it seems the best oils would be a waste of money for 5k changes. Are they? Would a good syn. blend be ok? If so, what weight? Thanks for any suggestions!