Performace hit when I add a fourth car

This doesn't really bother me but I can add up to 3 cars and not lose any performance but when I add a fourth car my fps drops from 25 - 30 to 15 - 20 and my GPU usage goes from 95 - 100% to 50 - 85%

 

What CPU?
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Though regardless, it's only 4 logical cores, not really guaranteed more than 3 vehicles

 

Oh, that did not come to mind, thank you!
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I have an i3-4160 @ 3.60ghz // 2 cores // 4 logical cores

 

If I remember correctly, each BeamNG car is assigned to one core of the CPU, so in your case, having 4 cars on a quad-core CPU is being the problem here. Possibly the only solution to this is to get a CPU with atleast 4 cores & 8 threads, as then you will be able to run more vehicles at the same time, with a lesser fps drop