Originally Posted By: SXE10
I recently swapped oils in my car, I had been running
Castrol Edge 5w30 for the past two years. Last service I decided I try the
Edge 0w40. Now looking at their KV ratings the 5w30 is 71.4 @40° & 12 @ 100°c. The 0w40 is 77.5 @40° & 13.1 @100°c. Based on this the 5w30 should flow better when cold right? But in the real world I find the 0w40 flows much better as I no longer have tappet noise on start up but could feel the 5w30 was better when warm (Hence I want to try 0w30 next). Now there must be more to KV ratings than meets the eye. I've read the Motor oil uni article which was great but it doesn't really delve into KV ratings as such.
Who can explain this better for me?
Thanks
Try 0W-30 Edge and you may have the best of both worlds!
Your 0W number is indicating better resistance to flow, as in not as much. The 5W may in fact have been great, but the 0W trumps it. The KV was less in the 30 so your engine did not have to use as much energy to spin it. People that put 20-weight oil in their cars (i am starting to become a believer, slowly but surely) have more power. Even read an article about a guy with a Civic hybrid from 2007 that put in two or three quarts 0W-10 oil and the rest 0W-20.. and it was amazing.
Your KV is not correlating to the 0W number, no direct connection. Frequently you can have a 0W oil with higher KV whereas you would think it would be THNINNER at temp due to the 0W. The W number and the second nnumber have no real relation.
Its all about how the oil is made, and who makes it.