[yco]

without a real inspection of the engine things can be just assumed but lower viscosity oils evaporate faster than higher viscosity ones and i dont think you re pushing the engine that much to evaporate over long period of time like hours in high temps.. you can compare the noack volatility of the car's oil if its the highest on the market.. and since its summer any problem with cooling can increase this..

but probably somewhere in touch with high temps was wearing out inside the engine minor but still.. if its multiple this can increase oil lose pretty much.. or if the car is not being used that much having short trips generally ending before engines optimal temp and you have a long trip or pushing the engine it can affect as well.. with those conditions oil can be diluted with fuel which can cause this.. or you re not waiting engine to warm up before pulls that can affect as well without noticeable smoke from the exhaust.. if you really want to know the reason only you can do is to reach manufacturer persistently to share the result with you though it can take months but anyways you ll know.. but i guess high potentially the reason is premature wearing out in the engine..