No Warmup Needed

Posted on in Todd Talks by Todd Johnson

When it's cold outside, as it normally is here in the dead of winter in the Northeast, scores of people walk out to their garage or driveway or push a button on their keys to warm up their cars. Some do it because they want a cozy drive, and some do it because they believe it's best for the car. But contrary to popular belief, this does not prolong the life of your engine; in fact, it decreases it.

To understand why warming up your vehicle is harmful, you need to fist understand how an internal combustion engine works. The pistons compress a mixture of air and vaporized fuel within a cylinder. This mixture is then ignited to create a little controlled explosion that powers the engine by pushing the piston down, which turns a crank and so on until that power is harnessed and used to turn the wheels.

When your engine is cold, the gasoline in it is less likely to evaporate and create the correct ratio of air and vaporized fuel for optimal combustion. Modern cars (since the late 1980s) use electronic fuel injection. These engines have sensors that compensate for the cold by pumping more gasoline into the mixture. This is called "running rich." The engine continues to "run rich" until it heats up to around 40 degrees Fahrenheit. So, if your car is just sitting there idling, this can become a problem because you're putting extra fuel into the combustion chamber to make it burn, and some of it can work its way onto the cylinder walls. Gas is an excellent solvent, and it can wash oil off the cylinder walls if you just let a vehicle sit and idle for extended periods of time. This washing of oil from the cylinder walls and piston rings can end up reducing the life of these components. This is due to the increased wear caused by the friction with insufficient oil to lubricate these parts. Additionally, when a vehicle is running rich, it's using more fuel, so you are losing fuel efficiency as well.

Pre-electronic fuel injection, vehicles were carbureted. These primitive devices were not as advanced and didn't use sensors to make the perfect mixture of air and fuel. Instead, carburetors relied on a mechanical system called a choke, which would limit the air that entered the mixture. It was a less efficient way to run rich until up to temperature, and it also made driving difficult and stalling out more likely. These older vehicles truly needed warming up, and a lot of people are still used to that. Some have even passed the practice down to younger generations.

Driving your car is the fastest way to warm up your engine. That doesn't mean get right in and drive it like you stole it. You should take it easy for the first five or so minutes to let the air-to-fuel mixture normalize. Some high-end vehicles even have rev limiters that prevent you from driving at full RPM until the engine is at the optimal temperature.

Another important and obvious thing to keep in mind is being able to drive safely. That means making sure all windows are clear of obstructions like ice and snow. I would recommend starting the car and then clearing the windows before driving away. Just don't use your heater to do the work. Your car will thank you.