The 10W-30 VR1 is only three viscosity points lighter than the SAE 40 VR1 @ 212 degrees (F), which is considered to be normal operating oil temp.

At 100 degrees (F), the SAE 40 VR1 is 59.8 viscosity points thicker than 10W-30 VR1.

The better flow of the 10W-30 VR1 at cold engine start-up (even at 100 degrees (F) will protect your engine better considering both oil viscosities at operating temp are so close.

In a street car, your motor oil operating temp (not to be misconstrued with coolant temp) will hardly ever see 212 degrees (F).