Can I use regular detergent in the WFW9250WW?

No, you must use only High Efficiency (HE) detergents marked 'HE' or 'High Efficiency' on the package. Using regular detergent will likely result in washer errors, longer cycle times, and reduced rinsing performance, and may also cause component failures and noticeable mold or mildew. HE detergents are formulated to produce the right amount of suds for best performance. (Page 12)