My guess is simple,first goal is to get Scott into the show.Speed Energy no Fast 5.Start and Test if Scott puts it in the show.Pit in the garage area.Just my guess.
Robby has two trailers. Trust me, you don't want 4 speed energy cars at a race, yet. RG's cars aren't where they need to be, yet. They're in survival/regroup mode. Sell more cans get better race cars. Right now you would just see 2 or more SPEED cars running around the back if he brought 4 cars to the track.