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.

Hell, multi weight oils start out at their low number and get more viscous as
their temp rises.

no they don't. 15W-40 is the same viscosity ("thickness" if you will) at "room
temp" as straight 15W oil is, and the same viscousity as 40W at engine
operating temperature. 15W-40 is much more viscous at room temp than it is at
engine operating temp. If you doubt that pull the dipstick on a warm engine
and see.

multi weight oils start out at their low number and get more viscous as
their temp rises.

Larry Berlin has been making that statement, but Larry seems not to have pulled
a dipstick on a warm engine in so long he can't remember. Or perhaps he is on
weight/blood pressure control medications and can't remember.

It is not true.

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

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

Interestingly enough, 15-40W is spec correct for both the mains and genset.

15-40W lubes a cold engine sooner upon cold engine start up than 30W or 40W
oil
does.

You can hear the difference.

While that maybe true, in this case we will not be seeing low ambient temps.
And if we were to, we would change the weight of the oil.

Capt. Bill

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

la bomba, you have smashed what little reputation you had left with your
question. Yet, you seem genuinely interested in the answer.

Yeah, right.

Unlike you I don't mind showing I don't know everything about everything.


Two problems exist with using a heavier than spec'd oil. first, and the
biggest problem, is pushing that cold, thick oil around upon engine startup.
It can take many seconds for pressure oil to get to the all the bearings
needing pressure oil. The thicker the oil, the more seconds it takes.

As I have said repetedly, we should not be seeing any low air temps. or engine
room temps.


Multi-weight oil was in fact expressly developed to reduce dry engine
startup's, particularly in colder weather. Original multi-weigh oils were no
over the long term as viscous as the oil they replaced, but the dry start
problem was cured. Today, most engine manufacturers recommended multi oils.
If you use a straight weight oil ***be sure*** to properly prelube the engine
before startup. Even with milti oils this ai good idea, with straight
weights
it is really important.

Many seem to disagree on the pelube issue. But I agree it can't hurt.


Second, straight weight oils that are tood supposedly can push out seals. So
I
have heard for decades but I never saw an engine that seemed to have lost its
seals due to anything but long use. Maybe it happens, dunno.

Never seen it.

Kinda third, heavier oils take more hp from the engine to keep itself
running.

Doubt that's much of an issue in this case.

Capt. Bill

PS, thanks for the reply. But next time could you write it before you start
drinking.

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

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

Hell, multi weight oils start out at their low number and get more viscous
as
their temp rises.

no they don't. 15W-40 is the same viscosity ("thickness" if you will) at
"room
temp" as straight 15W oil is, and the same viscousity as 40W at engine
operating temperature. 15W-40 is much more viscous at room temp than it is
at
engine operating temp. If you doubt that pull the dipstick on a warm engine
and see.

Perhaps I misstated. Multi weights oils, as I understand, when they get hot
only thin out to the point that their high weight number would at the same
temp.
Something about polymers uncoiling into long chains.

In other words think of a 15-40W oil as a 15W oil that will not thin more than
a 40W would when hot.

Like I said, that's my understanding. But, I could be wrong. That's why I asked
the question. :-)

Capt. Bill

15-40W lubes a cold engine sooner upon cold engine start up than 30W or 40W
oil
does.

You can hear the difference.

While that maybe true, in this case we will not be seeing low ambient temps.
And if we were to, we would change the weight of the oil.

"cold" is maybe 80* for engine startup while oil operating temps can be well
over 200*. 15W-40 lubes much quicker at 80* than does 40W.