English grammar can vs be able to

• You can use my car while I'm on holiday.

• You will be able to use my car while I'm on holiday –

is this sentence correct? Can we use "be able to" here?

Thanks.

You can use my car while I'm on holiday. Can indicates ability or skill or power to do something in the pedantic usage of the word. However, it is more likely that can is used to mean may here, and statement would be the same as: You may use my car while I'm on holiday. This would indicate that "you have (my) permission to use my car while I'm on holiday."

You will be able to use my car while I'm on holiday This sentence gives certainty that you using my car while I am on holiday is possible. Both of these sentences could be used, but the first sentence lays emphasis on the possibility on you using the car, while the second indicates the condition ( when - while I'm on holiday) when that is possible.

Some more information of using can and "be able to" under different contexts may be found on this link.