Susie Q & A: How long should I warm-up my vehicle before driving it?
Well, that depends.
The quick answer is, on current day vehicles, not very long. In fact some would say less than a minute or two. Since this is a subject that comes up frequently, and people are often in disagreement about it, I will try to provide a more in-depth answer. Hopefully, once you’ve read this article, you will not only know the answer, but the technical reasons behind it.
A little History
The gasoline powered automobile has been around since the late 1880’s. The early engines used a carburetor as the means to combine air and fuel for combustion. That continued up until the 1980’s, when the automobile industry gradually changed over to fuel injection. Today, the only carburetors you’re likely to find are on older models and race cars.
This is significant because engine warm-up procedures changed radically when fuel injection came along. Not surprising, old habits die hard and many people did not change their warm-up procedure as technology changed.
Why warm it up?
Air and fuel don’t like to mix when cold so warming things up helps with combustion. With a carburetor, the air and fuel have to travel a long way to reach the combustion chamber. When the engine is cold, fuel tends to condense on the cold surfaces of the manifold and cylinder walls. For this reason, a lot of extra fuel is needed just to get the engine started and keep it running. Delivering fuel at different throttle openings and load conditions was also a challenge for the carbureted engine, so trying to drive it without a proper warm up was difficult. It was not uncommon for the engine to run rough, stumble, or even stall after a cold start.
With fuel injection, the fuel is mixed with air just before the intake valve opening. It has far less distance to travel, fewer cold surfaces to come in contact with, therefore less condensation. This means less fuel is needed to start the engine and with on board computers, fuel delivery is far more precise. The result is better start up drivability, lower emissions, and shorter warm-ups.
It’s not just about the fuel though. During warm-up, oil is pumped throughout the engine, lubricating the bearings and other critical surfaces. When the engine sits for a period of time, much of the oil drains to the pan. As soon as the engine begins to turn over, oil is pumped throughout the engine, but cold oil is thick and hard to push into all the little spaces it needs to go. There is a risk of excessive engine wear without the proper lubrication. The good news is that oil technology has come a long way. Most vehicles call for multi-viscosity oil that’s been engineered to behave like thinner oil when cold and still have superior lubricating characteristics when very hot. This minimizes the need for long warm-up times.
So the Answer is..?
Little to no warm-up time is needed for modern day vehicles. Some will tell you the car can be driven immediately. Others say let it idle a minute to two before driving, about the time it takes to brush the snow off the windshield. Either way, what’s NOT recommended is letting the engine idle 10 or 15 minutes, trying to bring it up to operating temperature. Driving the car is actually the quickest way to warm it up. Of course, revving up the engine and hard acceleration shortly after starting, no matter what the temperatures are, is a bad idea and likely to be hard on parts. Keep in mind that these are general guidelines. It’s always a good idea to check your owner manual. Every vehicle is unique and if there are specific considerations or instructions, your owner manual will likely spell it out.
What about these?
Remote Starters: Many new vehicles come with a remote start option, and if they don’t, there are lots of aftermarket systems for sale. Remote starters use a transponder similar to a standard key fob, allowing you to start your engine without taking a step outside. What a great feature on a cold day. Not only does the engine have time to warm up, but some remote systems get the heater and defrost going and even turn on the heated seat function, if available.
There are some things to keep in mind, however. With a remote starter it may be tempting to start the vehicle up and let it run while you finish your morning coffee. Letting the engine idle for more than five minutes is not the best for fuel economy or emissions, let alone the life of your engine. Do NOT use this feature when parked in a closed garage, as deadly carbon monoxide can build up and overwhelm you. Depending on how the vehicle’s controls are set and how cold the temperatures are, remote start will also automatically turn on the heated seats, the defroster and start to apply warm air for the heater once it’s available. Once inside the cab you just put the key in the ignition, turn it, and your pre-warmed vehicle is ready to go.
Block Heaters: When you live where temperatures frequently go below 0 F (-18C), more than likely you have a vehicle equipped with an engine block heater. These can be factory-installed options or purchased through the aftermarket. The most frequently used block heaters plug into an electrical outlet and have a heating element that warms the engine coolant; some heat the engine oil. When it’s this cold out, the oil gets really thick and hard to circulate. Not only is this hard on the engine, as we discussed earlier, but it’s hard on the battery and starter motor as well. Using a block heater makes it easier for the engine start by warming the oil so it circulates better and reduces fuel condensation. An additional benefit is that it heats the coolant so you get heat and defrost working sooner. Although it’s recommended that the block heater be plugged in 2-4 hours before starting the engine, there is no significant change in recommendations for engine warm-up time once running.
So there you have it. Next time someone asks the question of how long should you let your vehicle warm up before driving, tell him or her if they read Throttle Gals magazine, they would know.