If you have a vehicle programmed to thermally castrate when the oil reaches a certain temperature, and the programming assumption behind that is that the oil in the sump is xw20, and you are of the opinion that that temperature is set lower for an xw20 than a heavier oil, isn't it counterproductive to use heavier oil even if you're racing?
Firstly, friction losses from heavier oil generate more heat, so the heavier oil will reach the higher temperature sooner. So you'll be thermally castrated sooner with a heavier oil than a thinner oil.
Secondly, the friction losses mean you're getting less performance from the heavier oil.
I'm not saying it wouldn't be desirable to have a thicker oil in conjunction with a higher point at which the engine is thermally castrated. What I am saying is if you are presented with a vehicle that was designed and programmed for an xw20 oil and you decide to track it then your only reason for using a thicker oil has to be that you don't trust the temperature at which the engineers set the thermal castration.
Firstly, friction losses from heavier oil generate more heat, so the heavier oil will reach the higher temperature sooner. So you'll be thermally castrated sooner with a heavier oil than a thinner oil.
Secondly, the friction losses mean you're getting less performance from the heavier oil.
I'm not saying it wouldn't be desirable to have a thicker oil in conjunction with a higher point at which the engine is thermally castrated. What I am saying is if you are presented with a vehicle that was designed and programmed for an xw20 oil and you decide to track it then your only reason for using a thicker oil has to be that you don't trust the temperature at which the engineers set the thermal castration.