Um – did you forget to include the 70% wasted energy that a car engine loses, due to various losses (mainly heat https://www.aaa.com/autorepair/articles/how-efficient-is-your-cars-engine )?
Your analysis works for electric cars, but not combustion engine ones, where most efficient speed for a mid-sized car is 55 mph ( https://tedb.ornl.gov/wp-content/uploads/2021/02/TEDB_Ed_39.pdf#page=137 ).