How much damage can diesel oil cause on asphalt concrete, and how can I get it off?

Question

I went on a holiday and my car has been leaking diesel oil and the caretaker in my building is threatening a large bill because of damage to the parking lot. How much damage does it cause, and how can I get it off?

Answer 1

It can cause deterioration of the asphalt.  The only way to get it off would be to scrub it off with a good grease cutting cleaner  and flood it with water.  But, once the damage is done, the only way to fix it would be to put asphalt or a asphalt repair down over top of it.  

Answer 2

Is is asphalt or concrete?

If the later, what you have is essentially a large stain; but if the former, then it is really messy. Asphalt is made with heavy fraction of distilled oil (e.g. tar) that binds a mix of sand and rock of various sizes (aggregate) together. Being exposed to a light oil fraction like diesel or gas, the tar is diluted and flows, freeing the aggregates. The asphalt that was thus exposed to diesel is finished, and needs to be replaced. That is indeed costly.