Oil stains on driveways not only looks awful but they are virtually impossible to get rid of. There are three main options:
Rust stains can normally be removed by using a liquid/mineral combination on the affected areas. Allow the active ingredients to take effect prior to slowly scrubbing with a bristle brush until the stain has gone. Ingredients such as, Vinegar, Salt, Baking Soda, Lemon Juice, Washing Up Liquid and Bleach can be applied in various combinations to achieve the desired outcome.
Unsightly and dangerously slippery; it also makes the whole place look dank and unwelcoming. Not really the sort of image householders want for their most important asset. Fortunately algae does little in the way of damage and can easily be pressure washed off any surface. Sometimes an additional water/bleach and other treatments may be required to remove stubborn stains.
Many people like the visual appearance of moss. However, left uncheck it spreads quickly and becomes a real problem. Under these circumstances, it can cause a lot of superficial damage to patio jointing, tarmac/block paving driveways and paths. Applying a liquid moss killing solution to the area some weeks prior to pressure washing, using a rotary cleaning attachment, is the optimum way to shift moss with minimal damage to surface integrity.
Chemically treat, burn with a flame gun, strim, salt/nuke them and they still come back. At best all one can do is manage the area effectively. This involves a number of processes that if applied regularly, will achieve the desired outcome. Root removal is the key but it is a long drawn out manual process. When the weed roots get in between patio joints and block paving they do serious damage and in a worst case scenario, the area will need to be dug up and relaid.
Pressure washing alone has little effect on these living organisms and an inexperienced operator can easily do serious damage to the stone surface. Once the area has been cleaned, the use of a strong bleach/water solution, applied and left for a period of time, will eventually kill off all the organisms. The process normally needs a number of applications before the infested area becomes completely clear but it is well worth the effort to get rid of the nasties.