Do Engines Really Run Better In The Cold? Here's What You Need To Know

If you've ever noticed that your car seems to run better in the cold, you're not alone. The internet is flooded with first-hand accounts of vehicles apparently delivering greater power and responsiveness when the outdoor temperature drops. It's a fair observation since, in many cases, engines will run better in cold air. However, as with all things, there are numerous factors to consider. There's a good explanation for why that happens, but it comes with several caveats, as well.  

Basically, cold air is denser than warm air and, therefore, contains a greater amount of oxygen. And because more oxygen means greater combustion within a combustion engine, the result is the aforementioned greater torque and responsiveness. Thus, tales of cars running better in the cold have real scientific explanations to back them. Yet while cold, denser air delivering better performance makes sense, it's not always the case. For instance, colder temperatures can also increase the viscosity of engine oil, giving it a slower flow rate. Altitude variations and your vehicle's fuel injectors will affect performance, as well. 

In fact, fuel injectors aren't affected by temperature, but their performance will vary based on their cleanliness. Indeed, you can clean your fuel injectors to improve their efficiency. In any case, it's one of the reasons why an engine's performance can vary, potentially leading to incorrect conclusions about factors like temperature. Also, air density varies with altitude, not just temperature, so a vehicle that climbs to a greater height above sea level won't necessarily gain a greater intake of oxygen even if it gets colder with the new heights.

Temperature isn't the only condition that will affect your engine's performance, which might explain why some of us don't get a performance boost when it gets cold. For example, higher altitudes often mean lower temperatures, but the thinner air reduces performance more than the density boost from the lower temperatures. Even fighter jets aren't free of the influence of air density, as the F22 Raptor's top speed varies drastically depending on its altitude. 

Consider a hypothetical. Take a trip from Sacramento, California, to Mt. Whitney, and you'll arrive at the mountain heights in about six hours. Travel from about 30 feet above sea level to about 14,500 feet above sea level, and in that short time, the average temperature will drop by about 12 degrees Fahrenheit. More importantly, however, the altitude increases from about 30 feet above sea level to about 14,500 feet above sea level. That higher altitude has a much bigger impact on the density of oxygen in the air compared to the relatively smaller temperature change. It gets colder the higher you go, but the atmosphere gets thinner as well. 

In fact, there are some ways that warmer temperatures can result in better engine performance. The US Department of Energy posits that cold temperatures decrease fuel efficiency and can make transmissions sluggish. First off, the USDE points to the increased friction within a car's transmission caused by cold temperatures. It also highlights how much longer an engine takes to reach a "fuel-efficient temperature" when starting from a cold temperature. If you take a short trip while starting in the cold, your vehicle will require a greater amount of fuel to reach optimal temperatures that run efficiently.

Hobbyists have found ways to take advantage of the improved performance that denser air provides. With a little clever engineering, they boost their cars' performance without needing to wait for the outside air to change temperature. It's actually a simple concept. Turbochargers are devices that compress incoming air before it reaches the engine's combustion. It relies on the same phenomenon that gives cold air its higher oxygen content — denser air leads to a greater concentration of oxygen. 

Another approach is to increase the intake of air. With a greater volume of air entering the engine, the air will be both cooler and hold a greater concentration of oxygen. This is one of the best mods for improving your car's mpg. It's called a "cold air intake system," and it works on the same principles surrounding air density and temperature. But such methods aren't a guarantee. One proponent of liquid cooling says this on a Reddit thread: "Stick a liquid O2 bottle under your hood. Boom, instant gains." You can choose to believe such internet viewpoints, and you might get some luck. However, the general consensus is that temperature is only one factor affecting engine performance.

The bottom line is that only risk-taking tinkerers will see an improvement in their engines' performances by modifying their engine bays with cooling systems. At the end of the day, most folks shouldn't expect significant performance increases when the temperature falls. In fact, some people may notice an improved performance with warmer temperatures as their oil increases viscosity. Thus, the idea that colder temperatures will improve engine performance can pretty much be written off as a myth since so many different factors come into play.