Modern automotive engines are no different than much older, carbureted ones in that they were both designed to deliver optimum performance and efficiency at their normal operating temperatures. As such, it is quite important to allow an engine to warm up to its normal operating temperature before gunning it down the highway. Let us explore the importance of warming up an engine from various viewpoints.
Engine Oil options: What you should know
Engine oils are designed to operate within a temperature range with consistent viscosity so that all moving parts within the engine are constantly lubricated. As long as there is no metal to metal contact, the engine should last a very long time. Viscosity is defined as the resistance of a fluid to flow, where the lower the resistance the better the oil. All engine oils available commercially come with an SAE viscosity rating, which defines its characteristics under various operating temperatures. In a nutshell, a 0W-30 rated oil means that the oil will flow considerably better at 0°C than a higher viscosity 15W-40 oil. The “W” or Winter rating is more important for countries that experience four seasons, but that doesn’t mean it won’t affect us in tropical countries. The second rating in the SAE chart is represented by a number, usually 30 or higher, to denote the viscosity or flow rate of the oil at 100°C, which is a typical operating temperature for a fully warmed up engine in a high traffic, start stop environment.
In the context of this article, it’s important to properly warm up an engine because viscosity is largely temperature dependent. In the case of a 0W-30 rated oil, its Dynamic Viscosity is 474.65 mPa.s (millipascal-seconds) at 0°C, thinning out to 38.008 mPA.s at 50°C. From this information, we can see that an oil flows more than 10 times faster at 50°C than at 0°C. At the other end of the scale, once the oil reaches optimum temperature (around the 90°C mark), the oil flows at 11.734 mPa.s. This information is especially relevant for today’s powerful high revving engines that require high flow rates to keep up with the valves, pistons and con rods. In my daily driver, a VW Golf TSi Mark 6, I have the luxury of an oil temperature gauge with which to monitor temps. It takes me a good 5-6 minutes of slow driving with the air-conditioning running, to bring the oil temp up to 70°C and beyond. For most cars that do not have a separate oil temp gauge, we recommend driving moderately slow for at least five minutes before taking the engine beyond 3,500rpm.
But your car has never experienced winter temps, so why is the W rating important? When you look at an SAE rating chart, you will see that there is a difference between a thinner 0W-30 oil and a thicker 5W-40 oil for instance. Ok, so let’s forget about 0°C for a minute. Looking at the official SAE rating chart, a 0W rated oil will flow 142.17 mPa.s at 20°C, while a 5W rated oil only flows at 206.89 mPa.s at the same 20°C, which is close to typical temperatures experienced by most Malaysian cars in the morning during a cold start. So, when taken into context of reaching optimum flow rates, a 0W rated oil will be able to reach the engine’s ideal flow rate a little sooner than a 5W rated oil.
A typical modern day automotive engine consists of a few major groups of components, each governing various aspects of the combustion and locomotion process, so when we talk about warming up an engine, we’re not just talking about the pistons and cylinder walls only, unlike what oil companies usually stress upon in ads. Aside from the obvious and most critical wear components, i.e., piston rings and cylinder walls, other components also experience a great deal of pressure once the engine is cranked to life. The engine’s connecting rods that link the pistons to the crankshaft are equipped with bearings that need proper lubrication, especially at high revolutions. If the oil isn’t properly warmed up, premature wear will ensue. And that is something car manufacturers won’t tell you, because your car only needs to last long enough until the next generation model comes along.
The gearbox in your car also has its own lubrication system as well to keep the gears from shearing one another. Transmission fluid is needed to keep the gears running like clockwork, and as such they too require some form of warming up to fully protect the cogs from premature wear. Gearboxes experience even higher pressures, so it is paramount to go slow from the get go.
So What Should You Do?
The underlying idea is not to stress your engine out and its various components by gunning it hard in the morning. All you need to do is turn the ignition on, wait a few seconds for the fuel system to prime, i.e., allow the fuel pump to feed the fuel line, then crank it up. There is no need to step on the gas pedal at this point because the car’s engine management system will take care of everything for you, unlike older cars with carburetors that needed a jab or two of the pedal to help it along. For cars equipped with keyless entry start stop systems, you can also practice the same procedure by not stepping on the brakes as you press the start button twice to bring the car into Ignition state which starts up the fuel pump and feeds the fuel line. Only upon the third button press do you then step on the pedal to start up the car.
You will notice that the engine will idle above 1,000rpm; this is perfectly normal as the car’s ECM (engine control module or formerly known as ECU – engine control unit) governs this process automatically to bring everything up to speed. The idle speed will slowly come back down, usually within 30 seconds or less, once the oil pressure is stabilized, i.e., oil is fully recirculating within the system. After another 30 seconds or so, you may shift out of Park and proceed to drive off. If your car is equipped with a water temp gauge, you will notice that water temps are still pretty much on the low side. Continue to drive gently, resisting the temptation to rev your engine above 2,500rpm. After a few minutes, and once the water temp rises, you may drive a little faster and switch on the air-conditioning. After about 10 minutes, every component within your car would have reached 90% of its normal operating temperature, and at this juncture you can safely jostle for position as you weave your way around the morning madness on the way to work.
In a Nutshell
If you treat the entire mechanical system in your car as you would your own body, it will reward you with years of faithful service without suffering the pains of premature ageing of components. You only need to ask yourself this question; if you had just gotten up out of bed, would you immediately put on your jogging gear and do 20 laps around the field without first warming up over a cup of coffee or tea? If the answer is no, then us car lovers at allcarschannel.com would recommend not doing the same to your precious ride as well. It’s really that simple. Most of the wear and tear that occurs to an engine, happen within the first 5 minutes of starting up your car, every single day.
Having said that, there’s also such a thing as taking too long to warm a car up, which is actually worse. If you allow your car to sit idle with the engine running for more than 5 minutes, you’re actually causing more harm than good, because the idea of driving off after a minute or so is to bring your engine up to operating temps as quickly as possible. The catalytic converter in your car will also be able to operate at its peak efficiency only after the exhaust temp reaches 300°C and higher, so if you left your car to idle, it will take a lot longer for the converter to start working properly to convert harmful exhaust by-products. So while you’re standing next to your car waiting patiently for the car to warm up, you’ll be exposed to harmful carbon monoxide, among other noxious substances coming from the exhaust. So do remember, start up, wait for a minute, then drive off slowly for about 5 minutes. That’s all there is to it, really.
Text: Greg Yang