GTA V weird fps fluctuations of each gameplay sessions

[lpio211]

• Hello. So i am getting weird fps fluctuations in GTA V. good cpu and gpu temps.
  
  *6700K stock
  
  *GTX 1080 Asus Strix normal clocks
  
  *Corsair 750 RM
  
  *For example. I drive in some always the same grassy area without traffic,without animals. In screen only my character and grass. Sometimes i get there 52 fps, another day in next session i have 46 fps. So there is anything in background. I tested with the same weather and daytime. And the same situation in other areas in game. Just sometimes i load game with 6 fps boost in any locations in game. Any ideas? Also no overheating, good temps in CPU and GPU. It is related to hardware or software? Ah i checked clocks of gpu and clocks are normal in both situations.
  
  Tested with 980 ti on my machine and the same. No overheating