There was a pretty major change for the 2020 model year, so for 2021, Audi hasn't done anything too drastic. First of all, every Audi A4 gets equipped with a mild hybrid system with 12 volts that gives the horsepower a little boost. Also, all of the A4 trims now have all-wheel drive. Other new features will be appreciated by many and can help the A4 stand out against the competition.