Should you warm up your engine in winter before driving?

Should you warm up your engine in winter before driving?

No! In most cases, warming up your engine in winter by idling it is actually bad for it*

Here are the cold hard facts about warming up your car in cold weather

• Idling to warm up a modern fuel injected engine is NOT recommended by any carmaker
• Idling warms up the coolant, but driving is what warms up the oil
• Driving with light acceleration for the first mile or so is the fastest way to warm up the oil and the coolant and the fastest way to get heat in the cabin
• You have enough oil pressure to prevent engine wear as soon as the oil pressure light goes out.
• Idling actually degrades your oil faster and causes EXTRA wear due to fuel dilution and soot production. This is especially true on gasoline direct injection engines
• Idling is not necessary and it’s wasteful

Why idling to warm up your car is bad for the environment and bad for your engine

Idling an engine to warm it up can actually causes more engine wear

A cold engine requires a rich fuel mixture and that extra fuel washes oil off the cylinder walls. The raw fuel and moisture from combustion gets past the piston rings and into the crankcase oil, diluting it and reducing its ability to lubricate. So idling to warm up your engine in cold weather actually causes more engine wear

Idling to warm up your car pollutes the environment— big time

Idling a cold engine for just 30-seconds produces more pollution than a warm engine produces in 100-miles of driving (proven with actual testing). So idling a cold engine is really bad for the environment.

Idling also doesn’t allow the catalytic converter to reach “light-off” temperature, so none of that engine generated pollution gets treated by the catalytic converter; it goes right out the tail pipe.

Idling your car wastes gasoline — a lot more than driving it to warm it up

Most late model vehicles are built with smaller engines that use turbochargers and direct fuel injection. Because they are smaller and hold less coolant, they warm up faster. Idling these engines until the cabin is warm just wastes fuel and damages your engine.

Idling degrades your oil much faster

If you read your owner’s maintenance guide, you’ll see that extended idling is regarded as severe service, requiring more frequent oil changes. Here’s why.

All engines produce blow-by; gasses that escape past the piston rings and into the crankcase. Blow-by from a cold start contains raw fuel that didn’t get burned, oil-wash from the cylinders, water (by-product of combustion) and soot.

Since it takes longer to warm up an engine by idling than it does by driving, you add more of those contaminates to your oil by idling. Exhaust gases, fuel, and water form acids in your crankcase that rapidly degrade the anti-corrosion additives in your oil. Plus, at idling speeds, your oil isn’t filtered as quickly as when you’re driving. So less soot gets filtered out.

Idling warms the coolant but does a poor job of warming the oil

Scientific studies show coolant is warmed by combustion heat, while but oil is warmed in the bearings. Idling produces little to no load on the bearings, so the bearings generate little heat during idling. See this article on oil flow in cold weather

Cold start advice from the Energy and Transportation Sciences Division of Oak Ridge National Laboratories

“Light-duty vehicles are ready to be driven at start up, and neither medium nor heavy-duty vehicles need long warm up periods. According to many original equipment manufacturers (OEMs), idling can actually be damaging to an engine and vehicle components. This is because idling can produce sulfuric acid, which can eat away at the engine and other components.

Additionally, idling results in lower in-cylinder temperatures combustion, which can produce additional soot, creates buildup in the engine, and causes unnecessary engine wear. Based on the potential for engine damage, drivers should avoid idling whenever possible. Generally speaking, more than 5 minutes of idling is excessive and should be avoided.” — Summary of OEM Idling Recommendations from Vehicle Owner’s Manuals
Energy and Transportation Sciences Division June 2016 prepared for the U.S. Department of Energy

What does your owner’s manual say about warming your engine by idling?

These carmaker comments were taken from the Oak Ridge National Laboratories Summary of OEM Idling Recommendations from Vehicle Owner’s Manuals

BMW: Drive away without delay. Do not wait for the engine to warm up while the vehicle remains stationary. Switch off the engine during longer stops, e.g., at traffic lights, at railroad crossings, or in traffic congestion. Drive at moderate speed for a short distance first, especially in cold weather.

Cadillac: Avoid idling the engine for long periods of time.

Chevrolet: Do not warm up the car. Even on the coldest mornings, the vehicle is ready to go in just 30 seconds. In fact, vehicles reach optimum operating temperatures faster when driven instead of idling. Operate the engine and transmission gently to allow the oil to warm up and lubricate all moving parts.

Ford: Don’t idle for more than 30 seconds. Today’s engines don’t need to be warmed up. Turn the engine off in non-traffic situations, such as at bank and fast food drive-up windows when idling more than 30 seconds.

Honda: Avoid excess idling.

Hyundai: Remember, your vehicle does not require extended warm-up. After the engine has started, allow the engine to run for 10 to 20 seconds before placing the vehicle in gear. In very cold weather, however, give your engine a slightly longer warm-up period.

Infiniti: Allow the engine to idle for at least 30 seconds after starting. Do not race the engine while warming it up. Drive at moderate speed for a short distance first, especially in cold weather.

Lincoln: After idling for a few seconds, release the parking brake, apply the brake, shift into gear, and drive.

Mazda: After idling for a few seconds, release the parking brake, apply the brake, shift into gear, and drive.

Mercedes: Do not warm up the engine with the vehicle stationary.

Nissan: Allow the engine to idle for at least 30 seconds after starting. Do not race the engine while warming it up. Drive at moderate speed for a short distance first, especially in cold weather.

Toyota: Avoid lengthy warmup idling. Once the engine is running smoothly, begin driving—but gently.

VW: Do not let your vehicle warm up while standing; instead, start driving right away after making sure that you have good visibility through all windows.

* Unless you’re still driving a carbureted vehicle. Then warm up is important. See this article on why warming up a carbureted engine is important

©, 2018 Rick Muscoplat