For Forza Horizon 5 specifically, the consensus among the community is . The risk of a permanent ban far outweighs the temporary fun of unlimited credits or god-mode driving. Unlike older single-player games, FH5 treats trainers as malicious cheating, not modding.

If you decide to use a trainer, here is the most conservative method:

It is highly likely that will migrate to a fully online economy where currency is calculated on the server, not your PC. This will render traditional memory trainers useless.