Jay from Laurel, Md writes
Per the 4-Speed XT product label: Adding oil, wetting agent, or other surfactant (such as Prime Source Duo Stick Select) to the spray may be done to increase effectiveness on weeds, but doing so may reduce selectivity to turf resulting in turf damage. Failure to observe the precautions may result in injury to turf and other desirable vegetation. Please review the product label for listed precautions.
Answer last updated on: 10/14/2019