Not sure if this is the cause, or related, or whatnot. But I'm going to tell it anyway. Because of a leak, I unknowingly ran my car today missing a gallon and a half of antifreeze. I got it fixed, and filled up, and it seems to be running strong. But I now notice a ticking sound coming from the engine. I don't know if it did this before, because you can't hear it with the hood closed. It sounds like my friend's engine when his lifters were ticking. Could this be the case on mine? It's a very quiet tick, that you can only notice with your ear close the the intake manifold. Is this caused by my own stupidity? Or simply by old age? Will running a thicker oil take care of it (I'm running 5w30 now)?