I may have put synthetic oil in my x type
 

is it bad for engine to use synthetic oil in x type.

xtype, putting synthetic into your engine is no big deal. As long as it was the correct weight oil, all is good. Potato, potatoe, same difference. You can theoretically flip flop between the two all that you want. From my experience, the gain of the full synthetic isn't worth the extra cost atleast in the short term. Depending on who you talk to, the full synthetics will make the motor last longer. But, some argue the other way. Take it for what it is worth.

The only real problem with switching to synthetic is that if you have any small oil leaks, they're going to get a lot worse because synthetic oils are thinner and find their way through cracks better..