and just what fricken surfaces in a diesel engine are "closer together" enough
so that 30W oil will flow and lube but 40W won't??????

If that were the case, those "closer together" surfaces would not get lubed at
all until the engine warmed up enough so that the cold 30W would flow.

Even the hydralic valve lifters on a gasoline engine (with some very tight
tolerances, down to a few thousands of an inch) would not operate (what a hell
of a racket you would hear) on 40W or not-yet-warmed-up-to-operating-temp 30W.

Oil too thick = may not lubricate completely between surfaces that are
closer
together, where the lighter oil is designed to flow.

this is not true in an engine. the difference is important during cold
engine
startup.

Are you daft? (retorical question)

BB

Subject: 40W oil causing wear problems over 30w?
From:

(LaBomba182) wrote:

Subject: 40W oil causing wear problems over 30w?
From:

But other than the warranty concerns, I'm I missing something here?
Would using 40W over 30W in the gensets with of course changing it at the
proper number of hours and making sure that the ambient temps never get
low
really cause any long term problems?


Yes it can.

OK, how ? In what ways?


The short version:

Oil too thick = may not lubricate completely between surfaces that are closer
together, where the lighter oil is designed to flow.

Oil too thin = surfaces may make contact by forcing out lubricant.

In this case I'm still not buying it. (at least not without much better
documentation)
40W is not that much "thicker" than 30W. And this is not a high revving engine
where oil film shearing would be a problem.

And to thin an oil is not an issue here.
Capt. Bill

In article ,
(JAXAshby) wrote:

snipped because I have another point to make


One other thing to remember in diesel engine operation, is
that the Base oil in a diesel engine is also designed as
part of the engines cooling system. Most larger (bigger
than 100Hp) engines have oil heat exchangers that run at the
temps of the cooling system. Oil Temps usually are 35 to
50 Degrees F higher than the cooling system temps found in
an engine. Today's Multiviscosity Oils are formulated to
allow for heat transfer from the friction parts out thru
the cooling system. Higher than normal oil Temps can
surely be a cause of concern, for premature engine failure
and something to be watchful for.


Bruce in alaska
--
add a 2 before @

Good choice on the 15W-40, but no, no , no on the last paragraph.

Oils most assuredly do NOT get thicker with increasing temp, even if
they *are* non-Newtonian fluids.
Multi-grades MEET the viscosity requirement( for their grade) at low
temps AND at high temps( usually 100degC).
But the viscosity, measured in either SuS or cSt, decreases with
increasing temps..

You may enjoy hopping over to www.bobistheoilguy.com and spending some
time there. I think you'll find it worth your while. You may want to
also consider Shell Rotella synth 5W-40, and asking your mfrs about
extended drain schedules.

--

"LaBomba182" wrote in message
...
| Subject: 40W oil causing wear problems over 30w?
| From: Bruce in Alaska
|
| (LaBomba182) wrote:
|
|| Thanks, I saw that in the eng. and genset manuals and that's what we
will end
| up doing. Filling the clean oil tank with 15-40W and keeping 40W in
bottles
| and/or pails for the trannys.
|
| Based on this I still can't see how straight 40W would hurt the
gensets in any
| way.
| As long as the ambient temps stay high.
|
| Hell, multi weight oils start out at their low number and get more
viscous as
| their temp rises.
|
|
|
| Capt. Bill

So which is easier on my engine, short period at high speed and load, or
long period at low load and speed?

Capt. jeff

So which is easier on my engine, short period at high speed and load, or


---------long period at low load and speed ------------?


Capt. jeff

Jeff,

The question you ask is simply to vague to provide a spacific answer.

The considerations come from:
Number of cold starts
Number of thermal cycles
Hours of operation at rated output
Hours of operation at idle only load
Hours of operation at less than rated output

In roughly that order.

A cold start is any time the engine gets cranked to fire. This
contaminates the oil and is the time of worst lubrication.
A thermal cycle is any time that the engine is run long enough to get to
operating temperature. This means that all those part have to push on
each other and side and move and it is how things leak or crack.
Hours of operation at rated load actually cause little damage, but it
should be the most common operating condition. This is when/where
piston rings and valve seats wear.
Hours of idle only load beat the bejesus out of the valve gear, and the
rings and pistons don't really fit because that only happens at rated
load.
Hours of operation at less than rated load, but enough to achieve proper
operating temperature will do the least harm. The question would be why
you are not using the engine as designed? Reserve power is nice, but it
is expensive as a first cost consideration (why most sailboat have just
enough power).

I hope this either gave you an answer that you understand or enough
information to phase another question. In the case of the later, I'm
here a lot - try again.

Matt Colie
See prior sig this date


Tamaroak wrote:

So which is easier on my engine, short period at high speed and load, or
long period at low load and speed?

Capt. jeff

Oils most assuredly do NOT get thicker with increasing temp,

agreed, even though I personally saw a man billed as a "training director" for
a large importer of diesel engines say that very thing. He got seriously
****ed when I asked him later via email if you had pulled a dipstick on a warm
engine any time in the last 40 years.

Here's the scoop. Mineral oil is a shape changer with temperature.
Thick as a lollypop, thin as water, depending on temperature.

If you were all fired up to reduce your stock hold, you could consider
synthetic. This has incomparably more temperature stability of
viscosity. But besides the expense, it's found to carry the
contamination less well, AND because it DOESN'T go thick as molasses
when cold, the surface run-off is greater.( Of course the initial
oil-passage fill-up and flow is much better too...)

So a synthetic and compatible mineral oil mix 3:1 would fill your
needs for a superior compatible product. Still not cheap though.

Brian W


On 12 Jun 2004 20:05:13 GMT, (LaBomba182) wrote:

OK, so I'm sitting around with the captain and his engineer friend on the new
boat I'm project managing/co-captaining and we are trying to work out how to
run the same weight oil in the engines, gensets and trannys so we only have to
fill the clean oil tank with one weight oil and not carry any extra buckets of
different weight oils with us.
The CAT engines and ZF trannys can use 40W oil as per their specs but the
Northern Lights gensets only recommend up to 30W oil. The CATs could run 30W
but only at 86 deg. ambient air temps. We will certainly be seeing higher temps
than that.
I tell the capt. and eng. that based on the ambient air temps we will be seeing
even with the Delta-T fans that if it weren't for a warranty issue I wouldn't
hesitate to use 40W oil in the gensets.
The capt. and eng. disagree. They start saying that running a heavier weight
oil could cause wear problems and make the engine work harder over time. And as
an example they compare it to what can happen if you use a heavy weight oil in
a high revving street/race car. I point out that this is a diesel not a high
revving street/race engine. They back off that point a bit but we still go
round and round in a civil fashion.
In the end we will end up putting 15-40W oil in the tank for the engines and
gensets (as per specs) and keeping some 40W in bottles for the trannys.

But other than the warranty concerns, I'm I missing something here?
Would using 40W over 30W in the gensets with of course changing it at the
proper number of hours and making sure that the ambient temps never get low
really cause any long term problems?



Capt. Bill

Subject: 40W oil causing wear problems over 30w?
From: Brian Whatcott

If you were all fired up to reduce your stock hold, you could consider
synthetic. This has incomparably more temperature stability of
viscosity. But besides the expense, it's found to carry the
contamination less well, AND because it DOESN'T go thick as molasses
when cold, the surface run-off is greater.( Of course the initial
oil-passage fill-up and flow is much better too...)

So a synthetic and compatible mineral oil mix 3:1 would fill your
needs for a superior compatible product. Still not cheap though.

Thought of synthetics. But there are warrenty issue with them.

Capt. Bill