Do not do anything to a bowling ball that your bare hand cannot stand. Dishwasher might be fine, but check the water temp, it should not be boiling hot. Hot tap water is a good temp benchmark, and safe, if you use it in a bucket and some drops of detergent to crack the oil when it oozes out of the coverstock, and you might repeat the process if need be.
Just do never put a bowling ball into an oven, because you cannot control the heating well - it comes only from one side/source, so you easily create tension between the ball's components. The charm of hot water is that it evens out the heat distribution and prevents over-heating.
Only thing that might occur is that some coverstocks change color - "bleaching". But this does not affect performance, and if you later put some polish back onto the ball or when it absorbs oil again, it should get back to normal looks.
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DizzyFugu - Reporting from Germany
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