Asphalt or Coal Tar?
Coal-tar oil products are the most popular kind of driveway sealants. They are more durable and more resistant to automobile oil and gas penetration. Gasoline and other petrochemicals dissolve asphalt over time. On the other hand, asphalt-based sealants are more environmentally friendly. They don't release high levels of volatile organic compounds into the air, and they don't irritate the skin as much as coal-based products do. Because of the environmental factors and added fillers, asphalt sealants are more expensive than coal tar sealants.
A low-end oil-based sealer covers about 400 square feet and cost about $8 for a 5-gallon bucket (2010). This goes on like a coat of thin paint, and lasts for only one season. The best grade sealers cost $15-20 (2010) for a 5-gallon bucket, but typically cover only 250 to 350 square feet of driveway, depending on the condition.
Hot or Cold Crack Sealers?
Good seal coating material will handle cracks up to 1/8-inch wide. It is important to fill these cracks, and the expansion joints between the asphalt and concrete curbs, to keep water out. Otherwise, the pavement base can erode and cause major damage to the driveway. Use the best crack filler you can find.
Hot sealers are best for filling cracks between 1/8 to 1/2 inch wide. These products work somewhat like hot glue. The sealant comes in large coils. You press the material into the crack and heat it with a propane torch or a heat gun until it melts.
Cold crack sealers for asphalt come in pourable jugs or caulking material for small cracks. For wide cracks, they come as a compound you spread with a trowel.
Most asphalt driveways need to be sealed only every three years, when fine cracks begin to appear. There are two real exceptions. One is in the South and in desert areas with harsh conditions. The other exception is when the asphalt turns gray. Gray asphalt means that the binder is deteriorating.
Some people like to seal their driveways every year to keep them looking new. For this, use a budget, non-filled sealer. Realize that a buildup of sealer will occur. This will eventually peel, and it can be tracked indoors. Sealer permanently stains vinyl flooring.
Repair cracks and holes in autumn. Let them cure over the winter. In the spring, hose off the driveway well. Apply a thin coat of sealer, regardless of the grade. One coat is best. Multiple coats of sealer do not protect any better than a single coat, and can actually cause problems with cracking and peeling.