What type of detergent must I use in the WFW9250WW?

You must use only High Efficiency (HE) detergent, which will be marked 'HE' or 'High Efficiency' on the package. Using regular non-HE detergent will create too much sudsing due to the low water levels, which can result in washer errors, longer cycle times, reduced rinsing performance, component failures, and noticeable mold or mildew. Always follow the detergent manufacturer's instructions for the correct amount to use. (Page 12)