The snowflake mode is for use dnruig below zero degree temperatures and for AGM batteries. The car mode can be used at all other times. Also, it is our understanding that Optima batteries are AGM so we are a bit unsure to what your battery is exactly. But if your battery is a GEL battery, then we recommend that the car mode be used on your GEL batteries, as these batteries are sensitive to high voltage.
The snowflake mode is for use dnruig below zero degree temperatures and for AGM batteries. The car mode can be used at all other times. Also, it is our understanding that Optima batteries are AGM so we are a bit unsure to what your battery is exactly. But if your battery is a GEL battery, then we recommend that the car mode be used on your GEL batteries, as these batteries are sensitive to high voltage.