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.