I am going to replace my oil as part of prep for a turbo. What is the recommended weight oil? Truck will operate in everything from -40c to +30c. where is the best place to get it?
-40c ...... is pretty cold temperatures.
5000cst oil will be OK for you. Because as i know the 5000cst is the lowest available viscosity for silicon oil.
Your jeep must be having an extra cover for the radiator too? Because when the temperatures are super cold, then its important to cover radiator to warm up the engine.