Four mature oak trees across the street from my house, have died in the past 2 (two) years. Is there a problem that you are aware of with mature oaks...Is it contagious...I have eight oaks on my property.

You would need to know if those 4 oaks died because of a systemic disease called oak wilt to know if your oaks need to of a concern. Both the White Oak and Black Oak groups can get oak wilt. Our weather the last two seasons may have played a greater role in their deaths that a disease. Being old, planted in stressful sites are important factors. Consider watering during stressful weather, fertilizing in the spring during active growth, watering late in the season as dormancy begins and having a certified arborist make a visit to determine the health of your oaks are good strategies.