Multi-Viscosity in DD (was Synthetic vs Dino)

[Jeff Miller]

To address your question, not necessarily answer it, a little about
viscosity:

Oil gets thicker when it gets cold, thinner when warm. This is a
normal characteristic of oil, and for it to do so is the standard of
viscosity. If it gets thinner when warm, at the same rate as the
standard oil, then it is considered a single-viscosity / single-grade
oil. If it thickens and thins less than the standard, then it is
considered a "multi-viscosity" or multi-grade oil. In other words, if
it is the thickness of a 50weight standard oil when hot, but only as
thick as a 10weight standard oil when cold, it is rated "10W-50".

This is a desirable characteristic and it is usually desirable to
have an oil change little or not at all across the useable
temperature range. To lessen the effect of heat on the oil, short-
chain polymers are added to the oil to keep it from getting as thin
when hot. These are called "viscosity modifiers". Essentially you
take a 10weight standard oil, add viscosity modifiers to lessen the
thinning effect when it is warm, and you can create a 10W-50 oil.

This sounds like the perfect oil, but the problem is that these
viscosity modifiers are very fragile, are not very useful in high-
shear applications, and have a short life. In fact a dinosaur 10W-50
oil on a cam lobe or other high shear part of your engine is
protecting more like a 10weight oil than a 50! Straight 30weight will
protect as a 30weight oil, starting to see why multi-grade oils can
be bad? You can count on the straight 30weight. Also the worn-out
viscosity modifiers can gunk up engines. These are the reasons for DD
not recommending/approving multi-grade oils in the 92-series engines.
It has nothing to do with it being multi-viscosity, everything to do
with how it becomes multi-viscosity. I will never run a multi-
viscosity dinosaur oil in any engine that I want to keep, too much
sludge and too little protection.

Enter the synthetics. Since synthetics naturally thin less with heat,
and thicken less with cold, they are naturally multi-grade. Mobil's
original synthetic Mobil 1 was produced with no viscosity modifiers
at all, rated 5W-30. Although some syn oils do use viscosity
modifiers to stretch the range or tailor them to specific ranges, not
much is needed as the oils can usually make most of the range
without. Also a thicker oil basestock can be used.

So without actually answering the question, and being as non-
technical as I can be, I hope that a little understanding of multi-
grade oil ratings helps.

I've said a few times, probably will again, but Holland Motor Express
here in Holland used to run their entire fleet of OTR trucks, DD 2-
stroke powered, on Mobil Delvac 1 (synthetic). I was told at the time
that the results were very positive: less fuel consumption, less oil
consumption, less un-scheduled downtime. The oil was not changed
between major service intervals of 250k miles, filters only. That was
many years ago, back when everyone ran 2-stroke Detroits. I don't
know if the oil is recommended or approved for use in the DD series-
92 engines, or whether Amsoil is. I have run: RedLine, Amsoil, and
Mobil Delvac 1 in all of my Wanderlodges. It costs more to buy, but
since I was able to extend my change intervals to 12months it offset
much of the extra cost and I had several gallons less used oil every
year.

- Jeff Miller
in Holland, MI


--- In WanderlodgeForum@yahoogroups.com, "" wrote:
>
> I use Mobil 1 in my auto's, Rotella syn 15-40 in diesel farm
tractors and diesel pu's[because of price], Mobil 1 syn. for diesel
is proly better.As for the DD, don't think we are supposed to use
multi weight oil at all, but prev owner was using the Amsoil marine
diesel znd it seems to work well. I did alot of checking and this oil
seems to have extremly low ash content which is what DD requires so
maybe it is ok. That said I don't like their marketing plan and for
most aplications I think Mobil is better. Going to keep using the
Amison in the DD and keep studying this, may need to use special for
DD engines straight wt.there seem to be different opinions about this
from the DD tech's.Marvin SkaggsBuffalo, Ky. 427161984 PT40--- On Tue
04/11, patticake592000 < sgureasko@... > wrote:From:
patticake592000 [mailto: sgureasko@...]To: WanderlodgeForum@...: Wed,
12 Apr 2006 03:37:53 -0000Subject: [WanderlodgeForum] Re:Re;
Synthetic vs Dino;
> All this talk about the two types of oil is very interesting. I
use Mobil 1, in my Dodge diesel, with good results. BUT, other than
Amsoil, what other brand and weight can be used in the 8v92. I'm
ready to switch! Also does NAPA make a synthetic type filter.
Steve Gureasko 90WLWB40 Ponchatoula, La.
> SPONSORED LINKS