STP Engine Flush is specially formulated to be added to old dirty engine oil just prior to an oil change.
STP engine flush breaks down the sludge and gum that has baked onto the engines metal surfaces. Thins the oil to allow for better draining and removes metal particles than just draining your oil.
STP Engine flush is safe to use in ALL Petrol or Diesel engines.
Don't put clean oil into a dirty engine.