[Vwdiesel] Risks of straight weight

[Shawn Wright]

On 11 Oct 2005 at 10:27, Val Christian <val at mongobird.com> wrote:

> Shawn,
> 
> Remember that the VI of multivis oils will drop much faster than
> with a straight weight.  

Val,

Could you explain the VI and how it relates to the Viscosity at a given temp? I think I 
read about it somewhere, but am a bit foggy on it.

Another strategy, if you are going to 
> do very high temp runs, would be to use the 40W oil.  However, I 
> would stay with the 30W during the initial breakin.  Again, I think
> your high demands on the powerplant, and the  cooling and lubrication
> subsystem, are such that you may be trading reliability for performance
> to a ratio that many might find unacceptable.

I won't likely push the oil to those temps again during break in, so I will stay with the 
30W. My goal is to upgrade things to improve both reliability and performance. :-) 
However, even if the engine only lasts 100k miles, the typical lifespan of the stock 
1.6NA in a Vanagon, that is about 10 years for me, and by then I'll be ready for a 
TDI... :-)
 
> FWIW, in aircraft, aircooled engines, we will see oil temps above
> your experience.  
> 
> I don't have at hand he performance data on the oils you're discussing,
> but the numbers seem reasonable.  Also, I'd have to check with our lube
> people to see what the rating temps are.  Remember that viscosity is 
> one parameter, lubricity is another.  I think you'll find that when 
> viscosity improvers are a high percentage of the blend, that the lubricity is
> less than with a straight weight oil. 

I seem to recall reading that most synth oils are good to 300F+, but don't recall 
seeing data for dino oils, either because I wasn't looking for it, or it isn't as easy to 
find... At one oil change per year, sometimes two, cost of oil isn't a big factor, but I 
would like to treat this engine right. At the moment, the 30W I'm running is Walmart 
house brand, mainly because it was all I could easily get my wife to pickup hours 
before we left on our trip. Hope this is ok...
Once the break in is done, I plan to use Amsoil 15w40 Marine & Diesel oil (unless I 
am convinced there is something better, plus I have 16 qts on hand), which is full 
synthetic, and worked great in the old 2.1L WBX, curing the notorious lifter noise, 
even with extended drain intervals. 

Shawn Wright
http://zuiko.sls.bc.ca/~swright
'85 Jetta D 
'88 Westy 1.6TD 5 speed
 (see progress at http://members.shaw.ca/vwdiesels)
'82 Diesel Westy