It depends on the meaning of the word “several.“ If you have five or more cars in service at the same time, you can’t use the standard mileage method for any of them. Also, there are restrictions on whether or not, and when, you may switch back-and-forth between the two methods, if you wanted to do that. Review IRS publication 463, chapter 4.
https://www.irs.gov/pub/irs-pdf/p463.pdf
