Autosave is a facility used to store automatic posts from the bloggers, of course this facility is quite useful when it is something that we do not want to happen for example a power failure, craches browser or shutdown computer automatically by the virus. This new facility works when we make a new post, the blogger will automatically save the changes within a few minutes.
If we're not working on the page we are able to post-Clik "publis Post" to save as a draft or Clik "Return to list of posts" if you want to restore the draft and return to the post pages.

But the auto save does not work if we did publish posts to your blog:

Note: Autosave does not occur when you are editing posts that have previously been published to your blog. This keeps your readers from seeing your edits until you're done with them. When editing a published post, you can click "Publish Post" to republish the changes to your blog, or click "Save as Draft" to unpublish the post and turn it into a draft.

From the auto save is unfortunately advantage of this facility can not provide the option turn off the service if we do not want to use it. thanks