CERANTHIA@aol.com wrote:
> Hi everyone,when I bought my M-35 from "Mighty Joe Young" he recommended
> Mobile Delvac 1300--15w 40,and I have to tell you that when it comes to
> M-35's Joe is the "MAN". I get incredible mileage, plenty of power and she
> burns nice and clean. On the way back home from the Weare New Hampshire rally
>
> I averaged 12.22 miles per gallon,I couldn't believe it so I checked my
> calculations three times--they were right!!! Thanks Joe!
You have a very good truck, and I'm happy for you. Just curious...
have you tried making the same trip, along the same course, under the
same weather conditions, using a different oil? If so, was your
mileage significantly different? Your truck gets great mileage for a
truck of its type, but how do you know that it's because you used
Mobil Delvac 15W40, rather than any particular brand of SAE 30 (or
whatever other grade is recommended for your weather conditions)? I'd
bet a dollar that the overall difference in energy losses due to
engine friction with different oils is very small compared to the
energy losses due to rolling friction and wind resistance; thus, it's
effect on mileage would be very small compared to the effect of, say,
a tailwind vs. a headwind. Wind resistance is HUGE compared to the
engine friction. Think about it: if you kill engine compression by
loosening plugs, injectors, or whatever (yeah, I know a deuce doesn't
have plugs, but I'm speaking generically here), you can easily turn
the engine by hand with a fairly short wrench, but it takes the full
output power of your engine at maximum governed speed to keep your
truck rolling at its top speed on level ground. Most of that is due to
air resistance, and most of the remainder is due to rolling friction.
A very small percentage of the losses are due to engine friction. They
learnt us that back in Engineerin' school.
That's why I insist that I see results from a properly-controlled
scientific experiment before I use a different oil than one that the
engine manufacturer recommended. Anecdotal evidence and testimonials
are meaningless. I've heard a lot of testimonials about various oils:
* "Truckers swear by it": So, what? Do truckers run several engines
under identical conditions with different oils, and then *measure* the
wear differences? Nope. I'm in trucking school right now, and I can
assure you that they only teach us to drive the truck, not how to tear
down an engine and measure component wear.
* "I use oil X, and my truck runs great!": So, what? Maybe you have a
very good engine. Does it run poorly with oil Y? Can you *measure* the
difference, under nearly identical conditions, with *no* other factors
changed? If not, then you have no factual basis to say that your engine
runs well *because* you use oil X.
* "My engine lasts much longer with additive N": Ok, bring out your
micrometer, microscope, and analytical balance, and show me. Note that
*all* of the advertisements I've seen for various additives present
*only* testimonials, and *none* of them presented any real technical
data. All of the data that I have seen, based on scientific
experiments, shows that all of the tested additives make engine wear
*worse*!
I don't dispute that Joe is Da Man. I've communicated with him many
times, I've bought the occasional 50-pound stack o' manuals from him,
and I've found him to be a very helpful, friendly and knowledgeable
guy, who really loves those big green trucks, and is happy to see them
go to good homes. However, with all due respect, Joe, have you
*measured* that 15W40 increases output power or mileage, or decreases
*measured* engine wear, under *identical* conditions in the *same*
truck? I understand that you live in an area that gets much colder
than my area (it rarely dips below freezing here, and it never snows).
Is your choice to use 15W40 more a matter of convenience, so you don't
need to change oil seasonally? I certainly mean no disrespect towards
Joe or any other list member, but I have yet to see anybody *prove*
that their favorite kind of oil is better, or even "not worse", than
the oil(s) recommended by the folks who *designed* the engine in the
first place. That's why I choose to select "definitely good enough"
over "maybe better, but maybe worse, nobody really knows".
-- Mark J. Blair, KE6MYK <mblair1@home.net> PGP 2.6.2 public key available from http://pgp.ai.mit.edu/ Web page: http://www.qsl.net/ke6myk/ DO NOT SEND ANY UNSOLICITED COMMERCIAL EMAIL TO THIS SITE
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