Synthetic oil is the best lube option for cold starting a vehicle. Period. If you live in a frigid climate – as in, most mornings start at sub-freezing temperatures close to -18ºC between the months of November and March, you’re going to want to seriously consider switching to synthetic motor oil if you aren’t already there. To understand the logic behind that statement, it’s helpful to understand the internals of a typical ICE (internal combustion engine) and the path that oil takes within the engine when it’s added through the fill hole at the top of the valve cover.