"There is no way you can change default search engine BUT it is possible to add other search engines. First off you have to change data saving to 'extreme' then go to any search engine site you'd want to add, let's say bing.com then press and hold the empty search box a window pops out and click on 'add search engine'. That's it. Switch back the data saving options and there will be a new option in the search box."
Although the directions are for ipad, it worked for me in the latest version of Mini on android