Free oil painting lessons are available at Study.com, Bill Martin's Guide to Oil Painting and Jerry's Artarama. Each of these websites offers basic instruction in oil painting from trained artists. Some utilize videos, while others use pictures and text to relay information about painting.
Study.com offers free oil painting lessons including a beginners course and lessons on landscape painting, different techniques and color hints. Bill Martin gives a complete overview of materials and basic painting information. He also includes four different painting exercises to get new painters started. Jerry's Artarama offers over 100 videos focused on oil color work. Many of these videos introduce techniques through painting specific objects.