Does anyone know what the drive train loss is in our cars? I can find it all over the internet for the 7th gen, but not ours. Idk how safe it is to assume that our drive train loss is the same or about the same as it is in the 7th gen.

Drivetrain loss for FWD is typically 10-15%.

There's no set amount it's a guess. What ^ he said is about as accurate as you can get.

Even dyno'ing the car won't exactly tell you because different dyno's read different.

i would say its slightly more than the 7th gen because the S54 is a much beefier and heavier transmission over the C60 (6 speed)