Rick's Free Auto Repair Advice

Should you warm up your car before driving?

Should you warm up your car before driving?

Here’s the simple answer: For most cars and trucks on the road today, 30-seconds to one minute is all you need to warm up your car in winter!

Here’s why idling is so bad for your engine and the environment

1) Idling a cold engine for just 30-seconds produces more pollution than a warm engine produces in 100-miles of driving. So idling a cold engine is really bad for the environment
2) Idling an engine wastes gasoline
3) Idling an engine loads the oil with raw fuel, water and soot. If you just drive a short distance after idling, the fuel, water and soot form sludge deposits in your engine and degrades the oil’s anti-corrosive additives.
4) Engines warm up faster when they’re being driven than when idling.
5) A cold engine has enough oil pressure and oil flow to protect metal parts as soon as the oil light goes out.
6) It’s a myth that idling your engine actually warms the oil. Driving warms the oil much faster than idling. Idling an engine only warms the coolant.

Why people think oil doesn’t flow in a cold engine

Amsoil has a youtube video that shows convention and synthetic oil being poured from beakers at -40C. The results show the conventional oil barely moving, while the synthetic oil flows! What you are seeing in this video is a comparison of conventional oil’s Kinematic viscosity compared to synthetic oil’s Kinematic viscosity. In other words; one oil’s gravity flow rate over another oil’s gravity flow rate.

But what does that have to do with your engine and cold weather oil flow? NOTHING! Because engines don’t use Kinematic gravity flow oil lubrication.

Engines move oil under pressure, not gravity. That’s called absolute viscosity. As long as you’ve installed the proper viscosity oil for your engine, you will get enough oil flow to protect metal components as soon as the oil light goes out. Oil pumps in modern engines are designed to pump enough oil to lubricate a cold engine.

People think idling is the best way to warm oil

It’s not. An engine at idle has minimal load, and minimal load generates very little heat. The fastest way to heat oil and increase flow is to drive the vehicle. Idling the engine only warms the coolant, not the oil.

The truth is, if you’re using the proper viscosity oil, it’ll start flowing within seconds after starting and you’ll have enough oil flow to start driving.

What about warming up for better fuel atomization?

Fuel injection vaporizes gas much better than older carburetors, totally eliminating the need to warm up your car. However, if you’re driving an older vehicle with a carburetor, you should warm it up enough to get warm coolant under the carburetor.

MYTH: Driving a cold engine causes damage and makes it wear out faster

Fact: 90% of engine wear takes place during cold startup. But that wear happens during the first 2-5 seconds after firing up, before oil pressure builds to minimum. However, once the oil light turns off, you have enough oil pressure to prevent wear.

If you believe that it’s best to let the oil warm up so it can flow better, then the last thing you want to do is let it idle. That’s because idling is the least effective way to warm engine oil. Driving is the most effective way to warm oil.

MYTH: Wait until the temperature gauge reaches the middle

Engine coolant temperature is NOT an indication of OIL temperature!!
Read that again. Coolant temperature is NOT an indication of OIL temperature!!
Your engine coolant may be up to operating temperature, but the 5 quarts of oil in you pan is still cold. Idling doesn’t warm it. In fact, on a cold day, you’ll lose MORE oil heat by letting your engine idle than you will by DRIVING it.

What does your owner’s manual say?

The owner’s manuals in late model engines with direct fuel injection state that you should be ready to drive in about 45 seconds. That’s about the time it takes clear the windows, buckle up, turn on the heat and radio. Then it’s time to DRIVE. If you’re uncomfortable with driving that soon, wait two minutes. But after that, you should put it in gear and go.

At that point you’ll have enough oil flow to fully lubricate both the high pressure fuel pump and camshaft. High pressure fuel pumps boost gasoline pressure to almost 2,000-psi. so they do need a few seconds of warm up time to get enough flow to the camshaft to prevent cam wear.
But on non direct injection engine, 15-30-seconds of warmup is plenty. But don’t floor it.

How to drive after you’ve started your engine in winter

Just because car makers recommend driving after starting doesn’t mean you can put the pedal to the metal. Start the engine and let it run while you buckle up, turn on the radio and defrosters. Then put it in gear and drive GENTLY for the first 3-4 minutes. At that point, you’ve got good oil flow and pressure.
• Avoid jack rabbit starts and heavy acceleration for the first 3-4 minutes.
• Avoid heavy acceleration.
Hammering the pedal on a cold engine, especially an engine with a turbo, can DESTROY the turbo and the engine bearings.
©, 2018 Rick Muscoplat


Posted on by Rick Muscoplat


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