Never in a million years did we think that the internet would debate the appropriate amount of time that’s ideal for a remote starter to warm up a car. Some folks believe that even a minute is too much, and others want the interior to be toasty and warm and are willing to let the vehicle idle for 15, 20 or even 30 minutes. Let’s talk about the physics of cold engine starting and why a little warm-up time can help get you on the road faster.
Engine Oil Science
There is a myth that whenever you start your car or truck, you inflict serious damage to the bearings, cylinder walls and piston rings because oil isn’t flowing. Modern engine oils are designed with adequate viscosity (thickness) and surface tension so they don’t completely drain into the oil pan when your car sits overnight or for a few days. Think of the fingerprints you leave on a stainless-steel fridge door. They don’t evaporate. That’s because the oils on our skin stick to the surface. The same applies to engine parts. If you want to test this, put a drop of cooking oil on your finger and touch a stainless appliance. That spot will be there until you clean it off with a degreaser.
If you put the car away for the winter and nothing moves for several months, there will be a bit of extra wear during the first start in the spring. However, so long as you drive your vehicle regularly, accelerated wear from starting isn’t an issue.
Modern engine oils include viscosity modifiers. An oil like 5W30 acts like a 5-weight oil at cold temperatures and a 30-weight oil when warm. The lower viscosity when cold helps it to flow better when it’s frigid outside. The W in the 5W30 stands for Winter. We got an email from a reader in mid-January informing us it was 49 below zero Fahrenheit near Edmonton, Alberta. It was 25 Fahrenheit in Anchorage! When it’s this cold, any fluid will have difficulty flowing. This doesn’t mean that you can’t drive your vehicle. However, it will take a while for the engine to warm up.
Ultimately, you’ll have to start your vehicle at some point if you want to go to work. So, a remote starter will give the engine a head-start in warming things up.
Transmission and Differential Warm-Up
Another argument against prolonged warm-up time is that the transmission and differential aren’t warming when idling. In the case of the differential, gear oil is usually 75W90 or similar in viscosity. After just a few revolutions of the driveshaft, every part in the differential will have a thorough coating. Just as with the engine, the lubricants don’t drain dry overnight or even after sitting for a few days or weeks. The oil coats the gear surfaces and the roller bearings. A colder, thicker oil provides more protection between gear surfaces. The only drawback to the differential being cold is that it takes more energy for the ring gear to move through the oil in the bottom of the case.
Most modern vehicles have a transmission cooler integrated into the radiator. Fluid lines from the transmission run up to connections in the radiator. A small heat exchanger might be in front of or behind the main core or a dedicated cooling channel and fins integrated between the engine coolant lines. Ultimately, once your engine is warm and coolant passes through the radiator, that speeds up the process of warming the transmission.
So if you don’t warm up your vehicle significantly, neither the engine nor the transmission will be warm. If you let the engine idle for a while, both will be warm. Worrying about one and not the other isn’t an argument against using a remote car starter.
If it’s 40 below, you aren’t going to go outside, start your vehicle, then put your foot to the floor and drive off like Roscoe chasing Bo and Luke Duke. On the other hand, you don’t need to let your vehicle idle for so long that every fluid in every system is up to full operating temperature. The latter is a waste of fuel since it might take 10, 15 or even 30 minutes. Vehicles with physically larger engines take longer to warm up. A big V-8 engine has much more mass to bring up to temperature than a 1.5-liter four-cylinder. Idling is the slowest way to warm an engine. It’s not doing much work, so less heat is produced.
Suggestions for Engine Warm-Up Time
Here are our suggestions for an ideal minimum warm-up time for your car or truck. Whether you’re using a professionally installed remote car starter or are just sitting in the vehicle in your driveway, our benchmark for a minimum warm-up time is to wait for the engine idle speed to drop. When you start a fuel-injected car from cold, it typically idles between 1,200 and 1,400 rpm. The idle speed when warm might be 500 to 900 rpm. The coolant temperature sensors in the engine directly control the idle speed.
Go to your car or truck on a cold morning, hop in and start the engine. Listen to the engine speed if your vehicle doesn’t have a tachometer on the dash. Note how long it takes for the speed to start slowing down. This time can vary from five or 10 seconds on a warm day to a few minutes on a cold day. The speed dropping is a sign of some heat in the engine. Whatever the time it took is a perfect time to let your remote starter warm up your engine.
For us, we usually remote-start our vehicles just before getting ready to head out. We still need to put our shoes or boots on, get our coats on, and grab our keys, wallet or purse, and laptop bag. If it snowed, then we can brush off the vehicle and scrape the windows. Most of us have the rear window defroster, heated seats and heated steering wheel controls integrated into our remote starters. They’ll have time to warm things up if it’s below freezing. This is more than enough time for the engine to warm up. You can hop in and drive off.
As always, be gentle with throttle inputs and try to keep the engine speed down until the engine is at full operating temperature. Exerting extreme force on the engine when cold isn’t ideal. The gap between bearings and journals won’t have stabilized yet. These gaps, measured in the thousandths of inches, are small but are critical to maintaining a proper fluid (oil) film. Letting the engine warm up ensures that the appropriate film thickness is present for adequate wear protection.
Tips For Cold Weather Engine Protection
Here are a few tips to make starting your car or truck on a cold winter morning easier and more reliable. First and foremost, if you haven’t already, switch to a synthetic oil at your next oil change. Even with the same viscosity ratings, synthetic oils flow better than conventional oils at low temperatures. Do you want a thick syrup in your engine or a fluid that will provide excellent protection?
Make sure your battery has a complete charge. We’ve talked about battery maintenance at length. Invest in an intelligent charger to keep your battery topped up for those cold winter morning starts. Every battery loses some ability to deliver current when cold, so keeping yours charged and in good health is crucial. Proper maintenance with biannual or quarterly reconditioning will dramatically extend the battery’s life and prevent you from being stranded.
Turn off any electrical accessory you don’t need in your vehicle. Most modern vehicles have a computer called the Body Control Module that shuts down things like the heater motor or radio when you crank the engine. However, in many cases, some of these items are left on for convenience. If it will be very cold out, turn off everything you can think of when you park the car. Turn off automatic headlights, the radio and so on. This will reduce the draw on the battery when it’s trying to crank the engine. If a local specialty mobile enhancement retailer has added heated seats, make sure they’re off while the engine is cranking.
If it gets extremely cold where you live, invest in a block heater for your car or truck. These small heating elements are installed in the engine block and warm the coolant. You can use a timer to turn the heater on a few hours before starting the vehicle. Likewise, a battery warmer might be a good investment if it’s frigid. A car dealership can often add a block heater to your vehicle. Remember to use a heavy-gauge extension cord with the heater to optimize its performance.
Make sure you have a set of good-quality jumper cables. If you have trouble starting the vehicle or need to help someone else, good cables (4 AWG or thicker) that are nice and long (20 feet) make jumping a dead battery much easier. Most importantly, if your battery has died, you must recharge it properly. This means more than running the engine for a few minutes. Invest in or borrow a high-quality battery charger with a desulfation or reconditioning mode and let it run a complete cycle on the battery. It should take eight to 12 hours to charge a completely dead battery back to its full capacity. The desulfation feature will stir the chemistry in the battery and restore or improve its performance.
Warming Up Your Car Adds Comfort
So what’s the bottom line on how long you should let your car warm up? Technically, a minute or two will be beneficial and allow the parts in the engine to build up some temperature. Do you need to warm your car for 15 minutes? We don’t think so. That’s quite a while, and you could run into trouble with anti-idling laws in your jurisdiction. When it’s time to add some comfort to your vehicle on a cold winter morning, drop by a local specialty mobile enhancement retailer and ask them about having a remote starter installed in your vehicle. Your cold hands will thank you for it!