Avoid switching thread types on your machine if you can possibly help it. An example would be to use polyester thread in black on one job and rayon thread in black for another job. The machine tensioners actually get used to one type of thread and like a child, it has fits when you make a change in its habits!

It is better to stick to one thread type. Your tension requirement for polyester is much tighter than for rayon and if you are constantly changing thread types; so is your tension and it is hard to keep a good consistent tension when you are switching types. If you find that you need to use a polyester thread for certain jobs, specify certain needles for those threads and use only
those for the polyester threads.

Polyester thread is safe to use on fabrics that will be bleached and on garments that will be sent to a commercial laundry but it does not have the sheen that the rayon thread is famous for.

It is best for your machine to be consistent with the thread type that you use and it is easier to maintain a more consistent even tension when you do stick to one type. This makes life a little easier and prevents a lot of needless headaches.