|
|
|
|
|||||
|
||||||
Subject: TWL: Re: Oil Weight
From: Alex Hirsekorn (alexh@XXX.XXX)
Date: Sun Apr 29 2001 - 02:05:11 EDT
----- Original Message -----
From: "Garrett Lambert" <e16@XXX.XXX>
> Currently running with 30 weight (120 HP
> Lehmans). Since I use the boat in the winter, I'd like to switch to a
> multi-grade, and the best deal on a quality diesel rated oil is for
15-w-40.
> Any reason not to switch?
Hi Garrett,
The last I heard, Bob Smith at American Diesel was recommending a straight
grade oil (30wt or 40 wt depending on climate) for Lehman engines.
That said; I wouldn't hesitate to use 15W40 in any four cycle diesel.
The advantages (real or perceived) of each type are as follows:
Single grade leaves more residual lubricant in place after engine shut down
because of the presence of "bright stock" which is a heavy residual blending
stock used in single grade oils but not in multigrades.
Single grade is usually cheaper. This could be changing because of that same
bright stock. This component used to be dirt cheap but its price has risen
approx tenfold in recent years.
Multigrade oils are thinner at low temperatures which means your starting
system has an easier life.
Multigrade oils reach the bearing surfaces more quickly at startup for the
same reason.
Multigrades are where the oil companies spend most of their R & D so you
tend to get the latest and greatest additive package in a multigrade oil.
Somewhere around here I've got a Chevron Technical Paper that describes
research proving that the use of 15W40 will result in lower oil consumption
compared to straight grade oils. Please note that this was NOT demonstrated
for heavy duty 10W30 oils.
Tribologically yours,
Alex
|