DNSChanger app
DNSChanger can be used to set DNS for mobile/WiFi network on Android phone.
Android has no option of setting DNS for mobile internet, so this app can help you to set DNS in that case.
This App requires root access as we need to use iptables. Advantage: No Android VPN technique, no battery loss.
If you are using OpenDNS server (208.67.222.222), you can verify it by using welcome.opendns.com and you should see successful message.