<html><body><div style="font-family: Arial; font-size: 12pt; color: #000000"><div aria-label="Compose body">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. "<br></div><div aria-label="Compose body"><br></div><div aria-label="Compose body">I might have that bass-ackwards. Didn't have time to look it up this morning.<br></div><div aria-label="Compose body"><br></div><div aria-label="Compose body">Bob<br></div><div><br></div><hr id="zwchr"><div style="color:#000;font-weight:normal;font-style:normal;text-decoration:none;font-family:Helvetica,Arial,sans-serif;font-size:12pt;" data-mce-style="color: #000; font-weight: normal; font-style: normal; text-decoration: none; font-family: Helvetica,Arial,sans-serif; font-size: 12pt;"><b>From: </b>"Bob Spidell" <bspidell@comcast.net><br><b>To: </b>"healeys" <healeys@autox.team.net><br><b>Sent: </b>Wednesday, June 10, 2015 7:47:33 AM<br><b>Subject: </b>Re: [Healeys] oil weight<br><div><br></div>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.<br> <br> I now use Valvoline VR-1 10W-50. Used Chevron 10W-50 for many years when it was available at Costco.<br> <br> Bob<br> <br class="moz-cite-prefix"></div></div></body></html>