You’re right, there are no V6 options for the Mazda 3. There is a turbocharged 2.5L engine that offers more power than the base engine, but that’s as much as you can hope to get out of the Mazda 3 without making additional modifications.
Mileage drops slightly with the turbocharged engine—but 35 highway mpg is still pretty fantastic.
If you’re looking for a V6 sedan, try the Audi A7 or the Toyota Avalon. The Audi is the most expensive with a starting MSRP of around $70,000 but it comes standard with a V6 and many luxury features you might like. Production on the Avalon ended in August 2022, but you may still be able to get your hands on a V6 with an MSRP of just over $36,000. For comparison’s sake, the four-cylinder Mazda 3 starts at $22,215.