The "B" designation refers to a mild-hybrid setup. The B4 FWD and B5 AWD are different setups that produce different results. The B4 FWD setup offers up to 197 horsepower, and the B5 AWD setup offers up to 247 horsepower and 258 lb-ft of torque. The B5 AWD setup is available on the 2022 Volvo XC60 for an additional cost of $2,300, and it offers a quicker 0-60 time but lower EPA-estimated mpg figures than the standard B5 FWD setup.2