How do you make a word plural that ends in o preceded by a consonant?

Some nouns ending in o preceded by a consonant are pluralized by simply adding es; these Words must be memorized, because there is no simple rule to explain the differences. Examples:

• echo, echoes
• hero, heroes
• potato, potatoes
• tomato, tomatoes
• tornado, tornadoes
• torpedo, torpedoes

There are also some nouns ending in o preceded by a consonant that simply add s; for example:

• auto, autos
• kilo, kilos
• memo, memos
• photo, photos
• piano, pianos
• soprano, sopraos