303 is for use on finished/coated leather as well as vinyl & rubber. I use it on leather after cleaning with Woolite & water. Superb product for every listed application. Unfinished leather, hard to find these days, should be treated with Lexol or a similar leather only product.
From 303 website:
"Most of the leather upholstery in domestic cars of recent vintage is plastic coated. The upper surface of such leather is ‘vinyl’.”
“Leather upholstery in most European cars is 'naked' leather which has no protective finish. The surface is that of the original hide. This leather 'breathes' and accepts conditioners applied to its surface.”
Dr. Jenkins explains how to tell the difference between “coated” and “naked" leather. Referring to coated leather he states, “Such leather can be identified by the failure of a drop of water applied to its surface to be absorbed into the leather after a few minutes.”
Contrasting the ability of naked leather to absorb conditioners (and water) with coated leather, Dr. Jenkins states: “While vinyl-coated leather is care free by virtue of its protective plastic surface, it is also inaccessible for purposes of maintenance.” Meaning, of course, there is absolutely no point to using leather conditioners on plastic coated leather.
So, how should plastic coated leather be maintained? According to Dr. Jenkins, “Such leather should be maintained exactly like vinyl upholstery.”