I added marvel mystery oil to my 250sx (in the oil) is this a good idea or should I change it?

 

Too late now, man!

Why did you add Marvel Mystery Oil in the first place?

Why do you now doubt your decision?

This product's been around a long time; as a minimum, I believe it will "do no harm," in the sense of the physician's oath.

I don't know what your expectations were when you added this lubricant to your crankcase, but I don't think it will hurt anything.

Tree Farmer