Kevin
Two parts per car to repair is really low. What level is your second account, what level is your manufacturing HQ, after which race did the cars only require 2 parts to repair and was it a wet or dry race?
In answer to your original post, in my opinion upgrading the manufacturing facility is worth doing but it's not the highest priority. Why don't you try not upgrading and see what happens?
Cheers
Kev.
My second account is level 14, and has a more upgraded manufacturing facility of level 6 compared to my level 3 manufacturing facility on this account. My lower level team with a higher manufacturing facility has to use more parts to repair the car than my higher level team with a lower level manufacturing facility