You must experiment with these list of DNS servers and see what's best for your location, if you find out your internet connection became unstable or slower you can revert back to your default DNS.
And here i provided the updated list of the best and fastest DNS servers you can use for free.
DNS Server Owner/Name, Primary and Secondary Address, Short Description
Google Public DNS
Primary server: 188.8.131.52
Secondary server: 184.108.40.206
Google operates the world's largest public DNS service. Launched in December 2009, it supports many billions of DNS queries per day, much of the volume generated from clients outside the U.S. The company developed this service as one of its corporate initiatives to make the Internet more accessible and easier for everyone to use, making it a logical choice for users worldwide.
Primary server: 220.127.116.11
Secondary server: 18.104.22.168
The oldest of all services on this list, OpenDNS also supports billions of DNS queries per day. In addition to its basic name resolution service, OpenDNS Home Solutions provides free Web site filtering of adult content (called FamilyShield) and URL spell correction with accompanying installed software. The company also sells various security products to businesses. Those looking for an alternative to Google products and a service that works well outside the U.S. also tend to like OpenDNS.
Norton DNS for Home
Secondary server: 22.214.171.124
Security software company Symantec began offering its free Norton DNS in 2010. The package works similarly to OpenDNS FamilyShield. Utility programs that automatically configure the DNS server addresses 126.96.36.199 and 188.8.131.52 and set up basic content filtering exist for Windows, Mac OS X and Android. Those already using OpenDNS or Google Public DNS but dissatisfied with those service can try Norton DNS to see how it compares.
Comodo Secure DNS
Secondary server: 184.108.40.206
In addition to its free DNS service, Comodo is known for the Antivirus package it sells along with other software products.
Secondary server: 220.127.116.11
A company called Neustar manages both the free DNS Advantage service as well as the commercial (not free) UltraDNS system.
Secondary server: 18.104.22.168
Designed to automatically block pornographic and other undesirable Web sites, ScrubIT made its debut in 2007 and received mixed reviews for its aggressive filtering policy.
Verizon / Level 3 CommunicationsU.S Internet provider
Secondary server: 22.214.171.124
Verizon maintains public DNS servers that can be used by both subscribers and non-subscribers. Verizon's servers (sometimes identified as "Level 3 Communications" or as "Genuity" / "gtei.net").