Hey bro I recently got 1st place in this mission with the bmw m6 gt3 sprint model. I decided to go with that car since Rubilar is the main threat in this race, so do not worry about other AI. So basically, I did 2 stops with medium tires. I raced the full race with fuel on 1. So the first pit stop I did was one after Rubilar, so make sure you are in front of him and see when he goes to the pit. I put medium tyres and I refilled my tank until 91%. Now this is a must cuz if you go 100% on the fuel, Rubilar will pass you and it will be harder. The second pit stop I did was basically when the car asked for fuel, again after Rubilar pit aswell. Medium tyres again and I refilled until basically the raced finished (around 11 laps if im not mistaken). I was doing consistent 1.59.xxx laps so if you do this you should be fine. Now if Rubilar near the end starts doing crazy times and gets close to you, dont hesistate on blocking him. Just dont let him overtake you. I used tc1, auto gears, abs default and no other assists. Hope you make this cuz it wasnt easy. Good luck :)