[Healeys] oil weight

Bob Spidell bspidell at comcast.net
Wed Jun 10 08:47:33 MDT 2015


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

On 6/10/2015 6:15 AM, John Rowe wrote:
> If you look at the description on the container (at least here in Oz) 
> the 5W-50 is for big bore flat tappet cam engines. That is a very apt 
> description of my 3000. The Castrol Edge Sport is the modern old 
> Castrol R, It's all to do with marketing.
>
> Cheers from West OZ
>
> John Rowe
> 1959 3000 BT7
> and many others.
>
> On 10/06/2015 9:03 PM, warthodson at aol.com wrote:
>> At our local club meeting last nite we had a discussion on motor oil. 
>> I had been using Castrol Syntec 20W-50 but I learned that they no 
>> longer offer that. They now offer Edge (formally Syntec) in 
>> 5W-50, 10W-40 & several other weights, but no 20W-50. Several of our 
>> club members are using the 5W-50.  Keeping in mind that we seldom 
>> drive in weather below 40 degrees F. What are your thoughts on using 
>> 5W-50? What weight oil do you recommend?
>> All of the above oils contain the zinc additive for classic cars. 
>> Also, Valvoline offers their VR-1 in a 20W-50 with the zinc additive.
>> Gary
>> Healeys at autox.team.net http://autox.team.net/mailman/listinfo/healeys 
>> Unsubscribe/Manage: 
>> http://autox.team.net/mailman/options/healeys/jarowe@westnet.com.au
>>
>>

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