Just about any vehicle is difficult to start in extremely cold temperatures, and your Jeep Cherokee is no exception. In regions of the world where the outside temperature commonly approaches or surpasses zero degrees, block heaters are very popular. Many different components are affected by the cold, and all of them can affect how the vehicle starts and runs. However, arming your vehicle with the proper equipment will make a big difference.
The chemical reactions inside a car battery that make it work all operate much more slowly in cold weather. Because of this, the battery gives less power to the starter, which makes turning the engine over a real challenge. For this reason, it is important to pay attention to the cold cranking amps (CCA) that the battery is capable of before purchasing, especially if you live in an area that experiences harsh winters.
Just like any other liquid, oil gets thicker when it is cold. When it thickens up and increases its viscosity, it is very hard for the oil pump to cycle it through the engine, which makes it difficult for the starter to crank it over. Synthetic oil does not have the same properties, however, and will remain thinner in cold weather, which results in turning the engine over more easily. While synthetic oil is more expensive, it might mean the difference between getting to work and staying home, frustrated.
When it is cold out, the fuel charge becomes much denser, which throws off the air/fuel mixture in a big way. Even the slightest change in the fuel charge can affect how an engine runs, so extreme temperatures really throw things out of whack. Although the cars of today have computers on board that compensate for air/fuel mixture changes, if it gets cold enough, any vehicle can be affected. That is why it is good to start the vehicle and let it idle for quite a while before motoring down the road. Allowing the engine to come up to operating temperature warms up the fuel charge and also thins out the oil quite a bit, so the vehicle will run smoother and more efficiently.
