New cars are way to taxing on your gpu. I get 90-120fps with the older cars but 30-45fps with these newer ones, on the same new track. The BTCC cars don't look that much better than the stock car 2018x for example, but the frame drops are enormous. Assetto Corsa i get 120fps with custom shader patch installed. In ACC i get 80fps maxed out settings. Automobilista i get 150-200fps. This is with about 16 cars on track.