If you are using the default address, then it can cause a lowering of the speed. It would be better to change your DNS to Google's public DNS server such as 8.8.8.8 and 8.8.4.4. Being said that, it will increase the speed so you can access the websites faster.
However, you have to keep in your mind that it would not increase the downloading speed when it goes to downloading large files or streaming online.