There are those who swear by using heavier-weight motor oil during summer months and lighter-weight oils during winter months for the maintenance of their car’s engine. In this day an age it’s sometimes hard to decipher whether or not they really know their stuff, or they are just pushing snake oil. Of course, as an article on the internet you also have to be critical of MY advice, but I have been doing it this for awhile (the whole car thing) and am prepared to offer you the science and theory behind the idea. So, in regards to an upcoming cold weather change, is this really the healthiest solution for four-season engine longevity?
Should I Really Use a Different Motor Oil in the Winter?
In short, research tells us that this is no longer necessary. Until about sixty years ago, oil was produced with only one viscosity measurement. Around 1910, the oil viscosity standard was established in a document called SAE J300. By 1926 there were six single grade SAE designations – 10, 20, 30, 40, 50, and 60, each graded for viscosity at estimated engine temperatures of 120 O and 210 O Fahrenheit. The higher the number, the thicker the viscosity at operating temperature. Oil would thin as it heated and thicken as it cooled – even to the point that very cold temperatures would thicken the oil beyond the point that it could properly lubricate the engine. Conditions like this made the use of different viscosity motor oils essential when seasons changed from summer to winter and back to prevent catastrophic engine failure. However, this problem was solved with the introduction of lower-temperature viscosity measurements around 1950 and multi-viscosity oils soon thereafter*.
Viscosity is the oil’s resistance to flow, or the speed of flow as measured through a device called a viscometer.
The thicker the oil, the slower it will flow, but the better it will protect when hot. Viscosity is measured in terms of kinematic (kv) and absolute (cSt) terms. These are made easier for us consumers by translation into SAE viscosity numbers that we see on oil bottles. There are two SAE ratings on all of our oil bottles that measure the oil’s different viscosities when cold and when hot.
The first number is the winter cranking (W grade). To get this number, the same oil is tested at 0O F to simulate a cold start on a winter day when the oil initially moves more slowly.
The second number is the high temp number (without the W). To get this number, the oil is tested at 210O F or 100O C, which is considered an average normal engine operating temperatures.
Together, the numbers indicate the difference in viscosity of the given oil between the time of a cold winter start and when it is warmed up to normal operating temperatures. So a 5W means that at a cold temperature, the oil flows at the same rate as a SAE 5 would under normal operating temperatures. A 5W-30 offers low-temperature engine protection in cold engines by exhibiting low viscosity equivalent to SAE 5 oil; whereas in hot engines its viscosity increases to SAE 30.
Synthetic oils bring another level of temperature flexibility. According to Popular Mechanics, although synthetic motor oils are really just natural oil refined to a much higher degree, performance-enhancing additives allow them to operate at an even greater range without breaking down as fast as conventional motor oils. High-quality synthetic oils are said to protect better over time, especially against extreme abuse such as very cold starts, towing or constant stop-and-go traffic. In addition, synthetic oils are made to better resist the high heat of turbo-charged engines (check out Adam Goral’s post on BIZOL synthetic oil for much more technical info).
Does this mean that you should abandon your time-tried habit of changing oil viscosities for winter in exchange for using fully synthetic oil year round? It may be an improvement, but be sure to first consult your owner’s manual and do your own research specific to your own car. Some auto manufacturers suggest a range of oil viscosities to suit different seasonal conditions, while others are more specific. In addition, some engines require fully synthetic oil while others are made for conventional. In the end, new technologies have made oil more flexible for a larger range of operating temperatures, but it’s up to you to pick what you use.
eEuroparts offers a full line of German-made BIZOL synthetic motor oils. You can find them by searching your vehicle’s make and model on eEuroparts.com.
Wow , that really cleared thing up, NOT!!!
I thought it was pretty clear. Don’t switch oil in extreme cold conditions unless your owner’s manual recommends it.
Shouldn’t it be beneficial to have a LOWER winter rating (less viscous) in cold climates?
Quote from article “5W-30 means that the oil flows like an SAE 5 when cold, and thins out to flow like an SAE 30 under normal engine operating temperatures.”
That’s backwards!!!!!!! SAE 30 IS NOT “thinner” than SAE 5
Sheesh, keep the day job.
You’re right! The article is wrong in that aspect.
Thanks for catching that, guys – I did mistakenly write it backward in the post, and it will be corrected soon. A lower viscosity number is less viscous. A 5W-30 offers low-temperature engine protection in cold engines by exhibiting low viscosity equivalent to SAE 5 oil; whereas in hot engines its viscosity increases to SAE 30.
I have a older ‘1989 Mercedes 190 E’. I still use the old 10-30W in my car.
Is it safe to switch to a ‘Full Synthetic Motor OIL’? Will the old seals and rings etc., etc., be alright ; or will my old car start using oil?
Thanks
Hey Larry, yes it is safe to use synthetic in an older car. If your seals are old and cracking, the switch to synthetic might result in a few leaks in seals that should be replaced anyway. Synthetic oil offers far superior protection and lubrication than standard class 1 and 2 mineral oils, with smaller and more uniform molecules that are good at getting into even the smallest spaces. So in general, will it cause leaks? Only if your seals already need to be replaced. Your engine will be happier as a result in the long run, but it’s understandable to stay with the older style oils if you don’t want to do a reseal. As far as we are concerned, this is just part of regular maintenance.
Thank you very much.
Have a “merry Christmas and a Happy New Year,”
Larry, good question. From what I have read, switching to synthetic motor oil is no longer as risky as it once was. When synthetic motor oil first came out there was concern that additives such as esters made it interact differently than conventional oil on seals – especially ones made of neoprene. Apparently that is no longer a concern with upgraded additives.
Check out this article on “How Stuff Works” for more info: https://auto.howstuffworks.com/switch-to-synthetic-oil1.htm
I find that almost all articles on mulit-viscosity oil, including this one, do a poor job of explaining how the oil actually performs at cold and hot operating temperatures (0 and 210F.) In other words, they kind of gloss over what multi-viscosity actually means in practical terms. Most articles say something along these lines: “When it’s cold, the oil will flow like a 5 weight oil; when it’s hot, the oil flows like a 30 weight oil.” Of course, if this were true, the oil would be *thinner* when you’re pouring it out of the bottle than it is when you drain it from your hot engine during an oil change, and we all know that’s not true, at least anyone who has added oil to a car and changed their own oil. Even in a mulit-viscosity oil, the oil is thicker when cold and thinner when hot.
So, here’s a better explanation:
When it’s 0 degrees F, a 5-30W oil will flow the way that a 5W oil would flow *when it’s at 0 degrees F*, and when it’s at 210 degrees F, it will flow the way a 30W would flow *when it’s 210 degrees F*. This does not mean that the oil is thicker at 210 than it is at 0, because a 30W oil *at 210 degrees* is way thinner than a 5 weight oil *at 0 degrees.* Just so, a 5 weight oil *at 0 degrees* is way thicker than a 30
weight oil *at 210 degrees.* But, a 5 weight oil is thinner than a 30 weight oil at 0 degrees, and a 30 weight oil is thicker than a 5 weight oil at 210 degrees. That’s where the advantage of multi-viscosity comes in: you want your oil as thin as possible at startup so that it pumps through the engine as quickly as possible, but doesn’t thin out so much at operating temp that it fails to lubricate.
Therefore, a 0-40W oil is always better than a 5-30W oil, no matter the season, because it offers a greater range in viscosity. Even in 120F ambient temps, engine oil is not hot enough at startup to offer optimal lubricity until the car is at full operating temp, so the 0W is an advantage. On the other end, 40 is always better than 30 because you have greater coverage on the hot end of things, perhaps with a tiny bit more internal resistance and power loss due to the greater viscosity of the oil at temp.
Lastly, full synthetic is always better, because the range in viscosity in synthetics is a product of the refining of the oil itself, and thus does not break down with age, whereas conventional oil achieves the properties of a multi-viscosity oil through the use of additives which are broken down slowly by the motor over the course of a 3,000 mile OCI.
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