1) Thank you unDummy for the excellent link to the document at Ethyl. Us Oil Heads can pore over that for hours.
2) Folks, there is an excellent discussion on the European Redline oil site (
http://www.redlineoil.co.uk/first.htm ) under FAQs of "What do the numbers on the oil can actually mean?" and "Should I use 'straight' oils rather than multi-grades?" that should help shed some light here.
3)
quote:
Originally posted by Gary Allan:
For example a 10w-30 is typically a 20 weight oil.
Where did you hear this? Do you have info on the straight weight basis of other multigrades? Apparently I have been mistaken to consider the "w" number as a rough approximation of the base oil weight. Look what the above quoted Redline Oil site says about it:
"Straight SAE 30 oil tested in such a fashion [the w grading tests] shows it is useable down to minus 10 degrees, thus this oil can be called an SAE 20w30. By adding viscosity modifiers to thicken the oil to an SAE 50 viscosity at high temperature then the oil becomes an SAE 20w50."
4) Let me throw more confusion into the works here by quoting an email response from same Redline Oil site:
" a 10w40 has got a thicker base oil than a 10w30 - indeed a 0w40 should have a thicker base oil than a 10w30 - and therein lies the next problem faced by an oil purchaser: many high street blenders start with say a 5w20 base stock and then add viscosity modifiers (which thicken the oil at high temperatures) to make 5w30, 5w40 and 5w50 end products. Because the viscosity modifers break down much more quickly than the base stock after a few miles you are driving around with a 20 weight oil in the engine rather than the 50 weight you thought you had! A good reason for using Red Line which uses a minimal amount of viscosity modifiers."
What is a "high street blender"?
5) Whew! Lunch is over. Gotta get back to work.
[ May 27, 2004, 12:08 PM: Message edited by: TallPaul ]
