You won’t be able to use more memory, as you are just deleting the cache.
I haven’t profiled it, but I would assume the performance might be affected in a negative way, since the memory has to be reallocated in order to be used again.
If you are seeing an OOM error, you could try to lower e.g. the batch size.
If that’s not an option, have a look at checkpointing 5 to trade compute for memory.