Oil Viscosity

[pls01]

The members response to the spin-on filter and lubricant threads spurred a comparison of oils.  The original 30wt is still good since most of these cars never start and operate at low temperatures.  Oil viscosity rises exponentially as temperature goes down.
   
      Viscosity in SSU
   
         Temperature
      50F   104F   140F   212F
   10W-30   793   328   182   56
   30W   1307   471   238   61
   10W-40   1367   521   274   76
   15W-40   1410   540   284   79
   20W-50   2369   810   396   95
   
   If a multi viscosity oil is preferred, the 10W-40 has the advantage of good flow characteristics at low temperature with better viscosity at operating (140F) and high temperature.
   
   The 15W-40 is also good because it is still available in API SJ formulation with the ZDDP high pressure additive.
   
   Peter

[pjbowman]

Peter - what brand(s) still have the ZDDP?
   
   Peter

[59 Aceca]

Peter and, uhm, Peter -
   
   Moss Motors sells an oil called Collector's Choice 20W - 50W with ZDDP.  Pretty good information on the site regarding its benefits. http://www.mossmotors.com/Browse/PlateMenuProducts.aspx?WebCatalogID=35&PlateTypeID=1&SubcomponentID=45&ComponentID=8
   
   Greg

[pls01]

Sorry about the table. It didn't come out as pasted.  The system won't allow spaces. The top row is temperature in (F) and should be pushed to the right a couple tabs
   
   The Shell Rotella T 15W-40 in API SJ formulation still has the ZDDP.
   
   I saw the Moss motors oil, but think 20W-50 is too thick compared to the original 30W.  At 140F, a typical operating oil temperture, 30w has a viscosity of 238 and 20W-50 has a viscosity of 396.  The high viscosity and high resistance to flow will produce higher oil pressure.  It will also cause less oil to flow though the engine and bearings.  More oil will flow through the relief valve.  Oil carriers away heat as well as lubricates.
   
   Keith has had good results with 20W-50.  It's hard to argue with success, but 20W-50 still seems a little on the heavy side

[pjbowman]

Thanks. Sounds like 10W-40 and some ZDDP additive might be the best approach. The Moss oil at $7/quart for an unknown brand seems pretty steep. I've always used 20W-50, but if I need to start adding ZDDP I may switch. I'm still a skeptic on the ZDDP impact, after all the hysteria on VSR that never seems to have occurred with unleaded gas.