I was able to vs I used to be able to

[Volcano1985]

Whats the difference?

[Esl_Expert]

Hello Volcano

When you use "was able to" you are probably referring to the ability to perform a single act at one specific time in the past:

Despite the fact that my arm was broken, I was able to swim to safety when the boat sank.

When you use "used to be able to" you are referring to a more general and regularly performed past ability, and it refers to an ability that you probably no longer have:

I used to be able to swim a hundred meters in under a minute. Nowadays I am lucky if I manage to swim that far in less than three minutes.