Lifters tapping in my car?

Unless it's very loud, I wouldn't worry about it. All OHC engines have some lifter noise. It may have started after the oil change because the new oil is slightly less thick, or because there is some air in the lifters (if they are hydraulic) after all the oil was drained. If they are mechanical, they may need adjustment. Either way, it's NOT a big deal, and your engine is not going to blow up. Wait a few days and see if it goes away before doing anything else. You could also add a bottle of STP, it works well for quieting noisy valves. Adding Marvel Mystery Oil will not help, and may make it worse, as it thins out your oil.