Annual cleaning is one of the few tasks necessary for vinyl siding and there are a number of products which can be used as homemade pressure washing detergent options instead of commercial products.
Dishwasher detergent or mild laundry soap dissolved in warm water will cut grease and grime which can begin to build up on the siding of a house. Be sure to rinse clean when finished.
Bleach or White Vinegar
Bleach should be applied to small sections where mold or mildew are problematic. White vinegar is better for large sections of siding. For either, 1 part bleach/vinegar to 2 parts water should be applied and thoroughly rinsed. Chlorine bleach is toxic to plants and animals even after it has seeped into the ground.
Standard, all-purpose cleaners (Windex, Fantastic, Armor All, etc) work well when diluted in 2 parts water. Bubble gum, grass stains, spider webs, dirt or bird droppings can be removed well. Never use nail polish remover, liquid grease remover, organic solvents or undiluted bleach on vinyl siding.