Does the persistence of mechanical grease, of which a small amount of color remains between the fingerprints and under the nails after it has been removed as much as possible, constitute a barrier that prevents ablution?

The grease used for lubricating car parts, if it forms a barrier preventing water from reaching the body, must be removed for every ablution (wudu') or ritual bath (ghusl (definition)). However, the presence of a small amount of it under the fingernail or on the hands, or the persistence of its color without its physical substance, does not cause harm. Indeed, a slight barrier does not pose a problem in any part of the body during ablution or ritual bath.