Or perhaps only an AI specific tire compound? This is coming up due to this video by Timo **** So I've been under the impression for years now that the AI was limited only to the softs. So using anything but the softs would give the player an unfair advantage due to not needing to make a pitstop, or suffering less tire wear. But I've gone ahead and tried it on my own, Formula Classic gen 2, and seemingly the cars can go a full race without needing to stop, where as I on the softs definitely needed to. Even with the mediums. So it could be that I'm over-driving the car and wearing out my tires.... or maybe the AI can indeed use mediums. Do we know for sure yet? Edit - I should note, to force the issue I was using x3 tire wear. By doing x2 tire wear it brings it all closer in line to expectations.
Unfortunately they only use the softs at the moment, the game compensates that shortcoming by making them last as long as the mediums or hards used by the player. But obviously is not ideal as there is pace difference between the compounds and they will have an advantage against the player or vice versa. Good news though, its on the pipeline to make them use different compounds in the race, finger crossed it comes with 1.6.