As I mentioned to George, after you elect the Standard Mileage Rate, you are not depreciating using MACRS (§168; see §168(f)(1) and the prior Revenue Procedure that I mentioned).

Although this is specifically referring to continuing to use the Standard (rather than Actual to Standard), there was a change or ruling a ways back that allows you to continue to use the full amount of the Standard Mileage Rate after it is fully depreciated.  Publication 463 says:

"If your basis is reduced to zero (but not below zero) through the use of the standard mileage rate, and you continue to use your car for business, no adjustment (reduction) to the standard mileage rate is necessary. Use the full standard mileage rate".

That specifically allows to you use the Standard (which includes built-in depreciation) after the vehicle is fully depreciated.

https://www.irs.gov/publications/p463#en_US_2023_publink100034059