even if used to emphasize that something will still be true if another thing happens even though used to emphasize that something is true although something else has happened or is true
even if used for emphasizing that although something may happen or may be true, another situation remains the same: He's determined to prove his innocence, even if he has to go to the highest court in the land.
even though used for introducing a fact that makes the main statement in your sentence very surprising: Most of us ignore this good advice, even though we know it to be true.
CALD
even if whether or not: Even if you take a taxi, you'll still miss your train.
even though Although: Even though he left school at 16, he still managed to become prime minister.
実践ではどうかな?次の文章は"even if"それとも"even though"にすべきか、 それともどちらでもよい?原点は、"Manual of Style for Technical Publications"
Messages should be clear, concise, and specific. Whenever appropriate, they should describe an action the user should take. When you write error messages, do not make the reader feel stupid or at fault, even (if/though) the problem is a result of user error.