Here are the full manufactures usage directions:
Before use, ensure any electrical components are protected, for example wrap in polythene.
Shake can before use and also during application.
Spray Gunk generously on the area to be cleaned until the area is completely wet. Leave for 10 minutes allowing Gunk to fully penetrate. If necessary, use a stiff brush to loosen stubborn deposits.
Rinse thoroughly with a strong stream of water.
Repeat applications may be necessary.
Do not use on hot engines or hot surfaces
Do not use on lacquered or painted surfaces otherwise discolouration may occur.
Gunk is not recommended for use on tarmacadam or asphalt surfaces.
Use appropriate protective clothing and face mask.
Do not breathe in spray or vapour.
Avoid contact with eyes and skin.
Keep away from sources of ignition.
Use in well ventilated areas.
Keep out of reach of children.