Ovih
Hello Barna,
I'll answer you based on what I understood from your question. The engine wears out in each race depending on the circuit and the PL you have during the race (the higher the PL, the higher the wear). The engine % is important during the races, because the lower the engine %, the less pace you will have.
You can check the state of the engine from the CARS window of the game menu or also from the NEXT RACE - SETUP window. From there you can see both the status of the car and the status of the engine (in %).
I'm not sure if this is the answer you were looking for. I see you've been playing for a year, so if you meant something else, please let me know.
Thank for the answer, I knew on what depend the engine wear, but I would like to know - of course only if it's possible - how calculated it concretely? (Concretely because in one of our league have engine limit and a rule that if someone exchanges reflexly (as with all other profiles), then it is possible to "neutralize" the switch with quick races, and for this we need to be able to tell afterwards at how much % they exchanged...)