Residual oil can remain relevant after washing and create a fire risk during or after heated drying. A visibly cleaner cloth is not proof that all contamination has gone.
Understanding this situation
The type of substance and appropriate handling instructions matter. A longer dryer programme does not decontaminate the textile, and a tight hot bundle can add concern after unloading.
A useful next step
Use the proper cleaning or disposal route for the material. Do not tumble dry unsuitable oily cloths or rely on a quick wash to make them safe. Report any related unusual heat or smell before the appliance is reused.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.