What should my Polygon Budget be?

Hello I am currently developing a Racing Game for Desktop. It will not just be cars, but also planes, motorbikes and F1 cars. There will never be any more than 8 cars in the scene at once. The environment will probably take about 200,000 polygons, but possibly more depending on the scene. I am aiming for an average Frame Rate of 30FPS +. Right now all of my cars are around 300K polygons. My question is what is the recommended polygon range for my vehicles in order to achieve my 30FPS goal while also keeping realistic lighting and high-poly vehicles Thanks Dok