Car covered in snow
Roadway Questions

Should I Let My Car Idle Before Driving?

I remember growing up and watching my parents run outside to “warm-up” the car before we went anywhere if the temperature dropped below 50 degrees Fahrenheit. In those days, they would let the car idle for at least 5 minutes. I never understood the concept of that. 

This guide will discuss the pro’s and con’s of warming your vehicle up and if it is necessary to let your car idle before driving it. 

What the Experts Suggest

If you ask an expert, “Should I let my car idle before driving,” you will get conflicting responses. Some say that you should when it is cold outside to get the fluids (specifically the oil) in your car moving. Others think that you can start it right up and drive it at speeds less than 45 mph.

Pros and Cons

There are some professionals that will tell you even if you have a fuel injector you should warm your car up for about 30 seconds before driving in subzero temperatures. Rather than preach about letting your car idle, I will cover the pros and cons of warming your car up. From there you can make an educated decision on what you should do. 

Pros

Allowing your car to idle: 

  • Helps the oil to flow in your car. When the engine is too cold, oil flow to other parts of the vehicle is restricted. Warming up your vehicle helps increase this flow.
  • Prevents cylinders and pistons from wearing out. When the oil is not reaching certain components of your car, because it is being washed away by gasoline. The longevity of these particular components is greatly reduced. 
  • Helps your carbureted vehicle run more efficiently. Unlike modern fuel injected cars, your vehicle runs more efficiently, and performance increases by letting your vehicle idle for a few minutes. 
  • Prevents your car from stalling out, because the air-fuel ratio mixture is enriched, rather than being too lean. It also helps prevent moisture or condensation from entering the vehicle or carburetor. 
  • Prevents low idles and rough vibrations. When you let your car idle, the engine heats up which makes everything run smoother.

Cons

When you let your car idle:

  • Will waste your gas. 2 mins of idle time equals 1 mile of drive time. If you let your car idle for 15-20 mins, it’s like you have already driven 10 miles. Doing this 7 days a week adds up. 
  • It puts a strain on your battery because it’s not getting a proper charge. Driving from Florida to New York, I stopped at a rest area to take a break and fell asleep with the car idling. Needless to say, by the time I woke up, my car battery was dead.
  • The performance of your car declines due to the wear it puts on cylinder rings, head gaskets, and spark plugs. Before you know it, these parts will stop working because they begin to deteriorate. 
  • It is harmful and poisonous. It pollutes the environment and it can be toxic due to carbon monoxide poisoning. 
  • You waste money replacing parts and getting more oil changes because you burn through oil more frequently. 
  • In major cities around the U.S., such as New York, Chicago, Boston, and others, will fine you, if you are caught idling longer than you should. According to the Environmental Protection Agency(EPA), you should idle for no more than 30 seconds, and drive your car. 

Vehicles Built Before 1995

Some experts will tell you that the answer depends on what year your car was made or if you have a fuel injector or carburetor. Cars made before 1995 will more than likely have a carburetor. Modern cars have fuel injectors that have multiple sensors to compensate for the extra air from the cold. 

Cold carburetors need to be warmed up before driving otherwise you may lose the performance of the vehicle. Carburetors are responsible for maintaining the proper air and fuel ratio, when mixed together properly it creates a vaporized fuel. If you fail to warm your carbureted engine before driving in the cold or snow, your engine isn’t getting the proper combo of vaporized fuel. 

Simply put- your car will stall and create other problems that you don’t experience when you have a modern fuel-injected car. Modern fuel injected vehicles are equipped with electrical systems that measure the ratio of air that goes into the engine. 

When fuel-injected vehicles were first designed, they were equipped with an O2(oxygen) sensor. This was used to manage and monitor the air-fuel ratio. Now there are multiple sensors that are more accurate and efficient at determining the air-fuel ratio. 

Tips For Idling

Whenever people ask if they should idle their vehicle before driving it, it is oftentimes, followed up with wanting to know how long they should let their vehicle idle. Once again this is one of those things that depend on the age of your vehicle.

Fuel-injected vehicles shouldn’t need to idle for more than 30 seconds. Some suggest that you start your car and put on your seatbelt and you should be ready to drive off.

Older vehicles require a longer and harder kick start. You can start your car and it should be ready to drive after scraping snow or ice off of your car. If this applies to you. Most car manufacturers and experts do agree that your engine warms up faster when you drive it at low speeds. 

Final Thoughts

To answer the question of, “Should I let my car idle before driving,” it’s your personal preference. You know your car better than anyone else(except maybe your mechanic). 

It has been decades since fuel-injected cars with electric systems entered the world. These days modern technology is constantly running tests, and car manufacturers are using the advancement of modern technology to develop innovations to improve the performance of cars. 

This is why modern vehicles do not require warming up before driving. However, to reiterate the choice is yours. You received the in’s and out’s about letting your car idle, you can use this information to decide if you will let your car idle or not.

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