Oft vs öfters

Can ‘öfters’ be replaced by ‘oft’ in the sentence below? Danke!

Das habe ich ihm schon öfters gesagt.

Question

Oft vs öfters

Can ‘öfters’ be replaced by ‘oft’ in the sentence below? Danke!

Das habe ich ihm schon öfters gesagt.

Answer

„Öfter“ is the correct expression. 
The superlative of „oft“ is „öfter“. Nonetheless, „öfters“ is used in colloquial language in Germany.

Answer

It‘s possible, but the meaning is slightly different.
oft = often
öfters = several times (btw öfter would be the correct form in this sentence, whereas öfters is only used in colloquial contexts)