# Oil... how does it work? \[split\] **URL:** \ **Category:** Shift518 Off Topic\ **Created:** [January 6, 2012, 11:40pm UTC](https://forums.speedlife.net/t/oil-how-does-it-work-split/262189 "2012-01-06T23:40:40Z")\ **Posts on this page:** 1\ **Showing post:** 100
**Author:** ![b-ri](https://yyz2.discourse-cdn.com/flex034/user_avatar/forums.speedlife.net/b-ri/32/6376_2.png) [@b-ri](https://forums.speedlife.net/u/b-ri)\ **Post date:** [January 9, 2012, 11:09am UTC](https://forums.speedlife.net/t/oil-how-does-it-work-split/262189/100 "2012-01-09T11:09:24Z")
> [@\--- GRAND THEFT AUTO IV --- Thread!!!](https://forums.speedlife.net/t/grand-theft-auto-iv-thread/47618/400): > > Vlad, reread the picture you keep posting. It clearly says that W designation oils are tested at 0 celcius whereas the normal viscosity rating is done testing the oil at 100C, just like everyone has been trying to tell you. You’re trying to argue two different rating systems. > > If you want to compare 5w40 to standard 40 weight oil you would have to heat them both up to 100C and compare. Comparing them at room temp doesn’t give you anything because they aren’t rated at 40 viscosity at room temp, they are rating 40 at 100C. Same as comparing 5w to 5, you’d have to compare them at 0C to have a valid comparison. Yes you get it. The sae weight number (ie. 30) doesn’t change in a straight weight oil. It has different viscocity at different temps… but the number does not change. A multigrade 5W30 has the properties of a 5 weight at 0_c (read: high viscocity but NOT AS HIGH AS A 30 WEIGHT AT 0_) AND THE PROPERTIES OF A 30 WEIGHT AT 100_C (READ HIGHER VISCOCITY THAN A 5 WEIGHT AT 100_). IT IS SO SIMPLE TO GET… THE NUMBER DOESN’T DESIGNATE A SET VISCOCITY. They are rated for their weight at 100\* c. The number does not change in a straight weight based on temp… the viscocity does… that is what vlad does not get. --- _[View the full topic](https://forums.speedlife.net/t/oil-how-does-it-work-split/262189)._