In order to lubricate a car engine, engine oil must remain viscous. The “W” in motor oil stands for weight. 10?

Wrong. In order to lubricate an oil must be able to flow to the bearings. A 0W or 5W will flow better at cold temperatures and therefore provide better lubrication upon start up in cold climates. Once warmed up the internal temperature of an engine is pretty much the same regardless of the time of year. So the top viscosity number in this day and age is required more by how close the tolerances are of the engine than by any outdoor temperature. Thus some manufacturers now recommend 5W20 oil instead of 5W30 because those engines using 5W20 are built to closer tolerances.





Use what your vehicle manufacturer recommends.





And the ';W'; does not stand for weight. It stands for winter.


The best oil in the winter in Canada would be Mobil 1 0W30 if 5W30 or 10W30 is recommended for your vehicle or 0W20 if 5W20 is recommended. I use 0W30 in my '96 Honda even though 5W30 is recommended and I use 0W20 in my '02 Honda CR-V even though 5W20 is recommended. These oils may be used year-round and it doesn't matter if you live in Canada or Mexico although they will protect your car more during cold weather in the North.





Thicker is Better Myth


The reason that oil viscosities have gotten thinner is because bearing clearances have become smaller. Using thicker oils will interfere with oil flow and the oil pressure will increase. In a worn engine it may be okay to increase the viscosity of the oil because the bearing clearances have become larger.In order to lubricate a car engine, engine oil must remain viscous. The “W” in motor oil stands for weight. 10?
Because you want the lightest weight possible for ease of starting. If your engine oil was say straight 30 weight all the time, then it would be a lot harder for the battery and the starter to even just turn the engine over, so hence chemically they alter oil to make it lighter. Then as the ENGINE heats up, the oil gradually get thicker up to the maximum specified on the bottle-give or take a small amount. It has nothing or very little to do with outdoor temperature, but engine temperature. It can be -20 degrees outside but if the vehicle has been driven at 60 mph for 3 hours the internal temp of the engine will be about 700 degrees.





Hope this answers your questionIn order to lubricate a car engine, engine oil must remain viscous. The “W” in motor oil stands for weight. 10?
A couple generations ago, oil was sold by straight-up weight. 30-weight, 40-weight. The higher the number, the better the oil's cooling and lubricating power, and the more it sticks to engine parts--and the more work it takes to move the engine parts through the oil. Most engines were built to run on 30 or 40 weight, so the oil won't break down at the engine's running temperature. But in a Canada winter, 40-weight is as thick as molasses. In the cold, when your battery is weakest, making the engine turn is just about impossible. So you use a multigrade oil, say, 10w40. At normal ambient temperatures, this oil acts like a 10-weight, but when it gets hot (over 150) it starts acting like a 40-weight.





Some cars owners manuals have a chart recommending what oil to use in what climate. You need 10w if you're going to be starting below 30 F. You need 40 if it's going to be over 100F. 30w is ok between 30F and 90F, or something like that.
the w stands for winter referring to the weight of the oil when it is cold. a light weight oil will get to the critical areas faster than a heavy weight oil. when the engine is warm oil viscosity will increase and there by increases the protection that it offers to loaded areas of an engine.
That is so it can efficiently lubricate your motor and transfer heat in all conditions preventing motor lock up from the oil freezing or getting so hot it loses its lubricating qualities.