'Why do I need to add sitemap to Google?' - Well, the short answer is : it will help Google to crawl your blog pages better and faster.
You can add your RSS feed to Google Webmaster Tools and Google will use it like sitemap of your blog.
How to add sitemap (RSS) to Google Webmaster Tools
1. Go to your Webmaster Tools2. Your blog mast be added to Google webmaster tools, if not - read previous article.
4. Go to 'Sitemaps' , and click 'Add a Sitemap'. Choose type: 'Add General Web Sitemap' and in the field put 'rss.xml' () . Click 'Add General Web Sitemap'.
5. Done...