spring offset shuttle valve vs regular shuttle valve

[yamajason]

At which oil viscosities do you think a vertically mounted shuttle valve can replace a spring offset shuttle valve. I have SAE 15w40 motor oil that ideally would go thru a 1psi Check Crack Pressure Spring Offset Shuttle Valve to prevent cavitation when the oil thickens at -20F degrees but most valves I have found operate on much higher pressures. This will be in a specialized automotive project that operates 4gpm 15-50psi at -20F to 250F temps. Please advise on valve selection