UTF8 and index speed/efficiency?

[Balthus Laurent]

Hello,

We are using mysql with a UTF8 for default encoding.
We have some tables with varchar and CHAR column having index on it. Those columns only contain some ascii characters (IE: 'Y', 'N', 'MONTH'...)

Would it be more efficient to force the encoding of those columns to be ASCII, so index won't use 3 times more space due to UTF8 encoding?
Could it make index search faster because sorting algorithm will be done on 1 byte per char instead 3 bytes?

Thanks for sharing your experience