[Vwdiesel] Risks of straight weight

[Gerry/Joy Wolfe]

To quote Bentley...
A2 diesels can use 15w40 about 0F thru 85F, minimum CD quality for a TD.

My understanding is that (say for a 15w40 oil) the base oil would be a 15w 
and would have viscosity improvers to make it look like 40w oil when really 
hot.  Generally, the closer the numbers are, the fewer viscosity improvers 
and the more real live lubricating stuff.

A question for the experts:  What percentage of the total volume of oil 
would viscosity improvers have to be to make a a straight 15W oil look like 
(15w)40 oil.  1%???  60%???  If it's only 1%, then there is still 99% of 
lubrication available in the mix.  If 60%, then I would guess the oil would 
only have 40% of the lubricating capacity of a straight 40W oil (ignoring 
any lubrication aspects of the additives).

Far as changes are concerned, oil doesn't really "wear out", but the 
additives do get chemically neutralized and the soot accumulates.  IMHO, 
'specially with a diesel, using a "cheaper" oil (meeting/exceeding the CD 
requirements) and changing it more frequently is better than using an 
overkill synth and not changing it as frequently.  This proved out to me 
recently... had to have a head gasket changed at 275K km and consequently 
had the head overhauled and a re-ring... there was virtually no wear/ridges 
in the cylinder walls, even the mechanic was surprised.  I do changes every 
3 months, Rotella 15w40 dyno.

Other hand, synth oil does a better job handling a hot turbo on shutdown - 
less prone to coking i.e. converting liquid oil into solid carbon (doesn't 
lubricate nearly as well next startup).

Just my $0.02 Cdn...
rgds, g.

----- Original Message ----- 
From: <LBaird119 at aol.com>
To: <vwdiesel at vwfans.com>
Sent: Tuesday, October 04, 2005 08:19
Subject: Re: [Vwdiesel] Risks of straight weight


> And for what its worth...What do you folks run, and at what temperature
> ranges?  I've been running 15W-40...mainly because that's what I can find
> that's diesel rated... in a hurry at the station.
>
>
>  I've always run Cennex 15W/40 year round, even when it's -20F.
> That doesn't happen much anymore but other than slighlty slow
> cranking on the COLDEST mornigns it does fine.  Pour point is
> the real thing on cold starts and it has a lower one than a lot
> of "thinner" oils.
>    Loren
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