For conventional 20W-50 engine oil, it will flow like a 20 Weight oil in cold weather, then with the viscosity of a 50 Weight oil once the engine is up to full temperature.
Choose Castrol GTX 20W-50 which is formulated to clean away existing sludge while preventing new sludge formation to help extend engine life. It is also liquid engineered to resist viscosity and thermal breakdown.
Inquiry - Castrol 20W50 4L