#narubeku

The meanings are really similar, but the nuances can be different. “narubeku" can be a bit weaker than “dekiru dake".

For example, 「なるべく走る」(narubeku hashiru) gives the meaning that you should run as much as you can, but you can stop when you feel like you can’t go on. On the other hand, 「できるだけ走る」(dekiru dake hashiru) means more like you should keep running as long as you have the power to. Saying it like this sounds really similar but basically dekiru dake sounds more.. demanding?

なるべく（narubeku) - as much as possible

ex. なるべく飛行機で旅行は避けています。(narubeku hikouki de ryokou wa saketeimasu) - I avoid traveling by plane as much as possible.

ex. なるべく早くていねいに書いてください。(narubeku hayaku teinei ni kaite kudasai) - Please write as quickly and carefully as possible.