Is it OK to put Mobil-1 5W30 synthetic oil in a 1993 civic with over 190,000 km (120,000 miles)? The car runs extremely well on Castrol GTX 5w30, but I am thinking of putting synthetic in it to protect the motor even more. The car doesn't burn or leak oil anywhere. My questions are:

1. Can it cause an oil leak to appear?
2. Can it cause the engine to start burning oil?
3. Is it worth the money?

Thanks.