How Long Should You Let Your Car Warm Up?

Since the advent of multigrade oils and electronic fuel injection, warming up one’s vehicle before driving has generally become less significant. However, this is not a blanket truth for all car types. Carbureted power mills still require idling. So, how long should you warm it up?

Regulatory bodies and experts suggest warming up your car for 20—30 seconds maximum. You may extend this duration for up to one minute but only in dire weather conditions (provided your car is carbureted).

Despite conflicting beliefs about how long warming up a car takes, the 30-second idling rule is universally recommended. Accepting and heeding it, however, is a different story.

If you have a different opinion about idling your car and are not quite convinced about the proposed duration, read on to get a better understanding of this fundamental practice.

Warming Up Your Vehicle

Even experienced vehicle owners get confused about whether or not to warm up their car due to existing myths surrounding the practice. Some believe it is necessary, while others do it only during winter or when temperatures drop before taking their cars out for a drive. These opposing sentiments have made it tricky for some to decide which of the two is the right course of action.

Idling Your Car Before Driving — A Myth?

It is not exactly a myth in its entirety, but parts of it are. When done accordingly, warming up your vehicle before taking it out for a spin provides benefits. But when done excessively, that is where the problems begin.

To drive this point further, you first need to get acquainted with which parts of the practice are ill-advised and their origins.

Some drivers warm up their cars for more than 30 seconds.

Sadly, this is where many owners slip — it comes from the belief that idling is harmless. However, nothing could be farther from the truth! Especially for four-wheelers 30 years or older, warming up their engines for more than half a minute only leads to unnecessary fuel waste.

According to a Natural Resources Canada study, warming up a car for longer than 30 seconds dramatically increases overall fuel consumption. At five minutes, it goes up by 7—14%. At double the time, fuel intake increases by 12—19%.

For carbureted vehicles, this would at least mean more frequent visits to the pump station. For fuel-injected wheelers, this would translate to an engine running rich and potential performance problems down the road.

Increased pollution is also another outcome of prolonged idling and is not one to be taken lightly. As reported in a 2009 study in Energy Policy, 1.6% of U.S. greenhouse gas emissions come from vehicle idling alone (sciencedirect.com). This figure is more than the percentage of emissions from the nation’s steel and iron manufacturing industry and is quite alarming!

Lastly, prolonged warm-ups strip the engine of its lubrication. When this happens, the engine becomes more susceptible to premature wear and tear. At best, you may be looking at more frequent servicing and oil change intervals.

Warming up the car is mistaken for idling the engine, as opposed to driving the vehicle for a few minutes.

A common blunder among car owners is the thinking that warming up the car is exclusively tantamount to idling it. This understanding is often why drivers are adamant about idling their vehicles for extended periods.

While I can understand why some people become stubborn with the concept, these two practices are nothing like each other. In fact, any car engine (whether gasoline or diesel-fed) will warm up faster by being at work (a.k.a. being driven) versus being put on idle.

Even EPA affirms this truth by standing by the 30-second idling rule. Except for really frigid days, excessive idling will not quicken the process of warming up your engine — so better to drive your car around than have it idling away.

Idling is believed to loosen up engine oil. 

This statement would have been absolutely true a century ago. But with the advent of SAE/ACEA/JASO parameters and multigrade oils, it is no longer the case.

The beauty of multigrade viscosities is that they work in weather conditions up to -40° F (-40° C). This means that an SAE 20W-40 motor oil will work the same way in ambient temperatures it was engineered for, regardless if you idle your car for 30 seconds or three minutes.

However, idling your vehicle for up to a minute in sub-zero weather does help in thinning out the motor oil inside the engine and enables a more seamless flow. But that is about the extent of going beyond the 30-second idling rule.

If you feel that a minute of idling does not suffice, pair it with driving around gently for up to 15 minutes to ensure the proper flow of engine oil.

Drivers idle or warm up their vehicles excessively to defog their car windows.

Of the four myth-based practices explained in this section, this is the most flawed, as it is the exact opposite of what actually happens. The longer you warm up your vehicle, the foggier your car windows and windshield get!

Prolonged idling is not the answer to everything. There are easy-to-follow steps you can do if you want to defog or defrost car your windows the right way.

How Long to Warm up Car

Now that we have got the myth-busters out of the way, let us answer how long it takes to warm the car up.

Ideally, it takes no more than 30 seconds to warm up your car before driving on an average winter day. Doing so within the prescribed time helps reduce driving detriments, such as pollution, window fogging, premature engine wear, and fuel waste.

But surprisingly, not everyone adheres to this.

A good number of vehicle owners are (for lack of a better term) still ‘fixated on’ the engineering of automobiles with old-school carburetion systems — pre-1990 models, to be exact. These cars relied on carburetors (view on Amazon) that required warming up to get the right mix of air-fuel ratio in the power mill.

The difference in operation between carbureted and fuel-injected four-wheelers is night and day. EFI-equipped vehicles, in particular, no longer warrant the traditional ‘engine warm up’ since sensors in the EFI system take care of getting the right air-fuel mixture to the engine and adjusting to temperature conditions accordingly.

The 30-second idling rule currently applies to all vehicle makes and models. And as established earlier, the only time this duration can be extended is when weather conditions are extremely frigid — or if your entire vehicle looks like the insides of a frosted, non-inverter freezer (view on Amazon).

The Real Purpose of Warming Up Your Engine

There is another good reason you should stick to 30 seconds tops when idling your vehicle (and no, it is not because of anti-idling laws in your state or township).

When asking yourself, “How long should I warm up my car?” the time spent idling should not be contingent on making your cabin warm and toasty. What you should be thinking of is the complete lubrication of your engine components. And believe it or not, 30 seconds is more than enough to get your car engine lubricated.

Some vehicle owners may disagree as they equate engine lubrication with in-cabin temperature. However, this isn’t the case. If anything, the inside of your vehicle may not even feel warm in the slightest by the time motor oil has coated all relevant engine components.

Hence, you should not go beyond 30 seconds since that is the only time your car needs for its engine to be lubricated. If you are after having toasty seats, the fastest way to do is by driving.

Key Pointers

When driving with a cold engine, still follow the 30-second idling rule (1-minute rule under exceptional circumstances) to give lubrication enough time to spread throughout parts of your engine. What you do after the warm-up is more important in frigid weather.

As a rule of thumb, gently drive for the first 5—15 minutes after starting your vehicle. Doing so gives your engine room to acclimate and get ready for harder acceleration.

Refrain from going beyond 30 seconds when idling — particularly when your four-wheeler is fuel-injected. Doing so is immaterial at best, if not wreak havoc on your engine components and EFI system.

For carburetor-equipped vehicles, the 30-second limit also applies to warming up the engine during summer. The same goes for gently driving the car for a few minutes after.

Older, carbureted vehicles require warming the engine up before driving in cold weather. Not doing so will result in excessive gasoline getting onto the cylinder walls, washing away engine oil from the pistons and cylinder and consequently leading to premature wear of these components.

For cars equipped with fuel injection, there is no need to warm up before driving — although gentle driving for the first few minutes is still advised.

Regardless if you have a carbureted or fuel-injected vehicle, use the correct viscosity grade for your engine oil. Even if you follow the 30-second idling rule, using the wrong SAE rating will cause the engine oil to not flow through the components of your power mill.

Conclusion — How Long Should You Let Your Car Warm Up?

Undeniably, there is a grain of truth to all the myths covered in this guide. As such, it is understandable why many car owners and mechanics still maintain the need to warm up their vehicles for more than a minute before driving (especially in cold weather).

However, it would be folly to follow the U.S. average of five minutes when idling. This duration results in more problems than solutions and does nothing to improve vehicle performance or engine oil fluidity during winter.

Given these outcomes, it would be best and most economical to warm up your car for at most 30 seconds. Not only is this sufficient time for lubricating your car engine, but it is also a surefire way of saving up on unwarranted fuel expenses.