Originally Posted by Christian and Beccy
LOL.
4th is the ideal gear, but 5th isn't too sad. Its just down to knowing how to read the graph.
The only legit reason to run it in 5th is for traction (i.e. if there was a lack of it in 4th).
To add to that - if you get a power at the wheels figure, the same car run in 3rd rather than 4th will show more. ( and the opposite - same car in 5th will show less ATW than in 4th)