good explanation, but you got them backwards. 75w90: the 75 is the "winter" weight. yes cold will "thicken" the oil, but the weight of the oil (as dealing with viscosity and "cling" effect, as well as several other properties) is lower to easy the stress on mechanical parts during start-up or initial movement.
once the oil reaches operating temperature, it will actually alter on a molecular level and increase viscosity and other properties of the oil to decrease wear, improve sealing and several other purposes of oil...
i used to work for valvoline and had to take an extensive class on this.
this is the same for regular motor oil, gear oil etc.
that is why running a 5w30 (depending on application) is much better than a 10w30 or straight 30 during winter: it save massive wear on parts during start-up/initial movement.
there are also several additives put into motor and gear oil (yes even non-synthetic ones) to aid in these properties.
another interesting thing about oils; synthetic vs. conventional- there is actually no oil that is "synthetically" made, it is still just crude oil, that is further refined, and normally including more or further advanced modifiers than the ones added to conventional motor oil.
if theres any other questions on this, lemme know, got alot of info on the subject (even got to go on "undercover" tours of other oil companies. lets just say, yikes! at what some companies put in their oil...)
back on subject now
