[Healeys] oil weight

[Bob Spidell]

re: "The VIs are long chain polymers that, when cold, are in more-or-less in straight lines but 'curl up' when hot to increase the viscosity of the oil. " 

I might have that bass-ackwards. Didn't have time to look it up this morning. 

Bob 

----- Original Message -----

From: "Bob Spidell" <bspidell at comcast.net> 
To: "healeys" <healeys at autox.team.net> 
Sent: Wednesday, June 10, 2015 7:47:33 AM 
Subject: Re: [Healeys] oil weight 

I'd stick with 10W-50 if you don't need the cold weather capability. The bigger the 'viscosity gap'--e.g. 5W-50 is 45, 10W-50 is 40, etc.--the more VIs (viscosity improvers) are added to a base oil. The VIs are long chain polymers that, when cold, are in more-or-less in straight lines but 'curl up' when hot to increase the viscosity of the oil. The bigger the 'gap' the lower the viscosity of the base oil--10W-50 might have a base viscosity of 7, for instance (just an example, I don't know the exact number)--and 5W-50 might be 3, etc. The VIs get 'sheared' in use and the hot viscosity goes down as a result. At one time, at least, 10W-40 was recommended against by some car manufacturers (BMW, I think), though my father has used it for many years with no problems. 

I now use Valvoline VR-1 10W-50. Used Chevron 10W-50 for many years when it was available at Costco. 

Bob 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/healeys/attachments/20150610/ab1815d8/attachment.html>