Non-synthetic oils thicken rapidly as the temperature drops. In cold weather, this causes difficult starting as the engine fights to turn over against the semi-solid lubricant. And even if the engine starts, the cold, thick oil will not circulate immediately, which means some parts of your engine can run for up to five minutes without any lubrication at all! AMSOIL Stays fluid at much lower temperatures. In cold weather, AMSOIL permits easier starting and instant lubrication throughout the entire engine. During starts and warm-ups, critical engine surfaces slide, protected by a tough, reliable film of oil between them.