A lot of times... Ebony is dyed with a black fgrain filler... to give it an extra black look... and also to fill in the grain so that it doesn't soak up as much moisture... So... I would say treat ebony as though it were maple... It wouldn't hurt it if you applied lemon oil... it just most likely will not help. But most guitars under the $1000 range that have Ebony fretboards are dyed.... Because they don't use a choice cut of the wood for lower priced instruments....