After the 1994 earthquake here in LA, I had to put in a new driveway. I sealed it with Seal-It concrete sealer (1995). Now (2010), it still looks like it did when we applied it. This despite having numerous oil & grease spills which we let “nature” clean up (in other words, just the small amount of rain we get & the sunshine of which we get plenty) the mess. Amazingly, nothing penetrates the concrete and we are supremely happy with the results, especially after 15 years!