Re: [a/s] Synthetic Oil

[Doug & Judy Stracener <ka5ysy@xxxxxxxxxxxxx>]

Hi Steve:

I use Mobil-1 in my wife's Chrysler Concorde, and Mobil Delvac-1 in my
Tahoe diesel. All the differentials and transmissions in both vehicles
are synthetic.

Why use synthetics:

1. Much better heat survival of of oils. Synthetic does not tend to
boil off like petroleum base oil. The oils are superior in all
respects in high temperature environments such as heavy duty towing
situations. In snow areas, synthetics are designed to flow much easier
when cold, than petroleum oils. Generally you will notice an SAE 5w-xx
or in some instances 0w-xx ratings. Result here is that the engine
will spin faster when cold and start much easier (easy on the battery
and starter) and give oil protection nearly instantly. 

2. Longevity; Most synthetics are capable of operating at much longer
change intervals than petroleum oils simply  because the polymers that
make up the oil do not break down as quickly as the petroleum
molecules in use. There are special "dual-bypass" filtration systems
available from Amsoil and other manufacturers that give the capability
of using synthetics over 100,000 miles without a full oil dump. This
is done by changing the filters and adding makeup oil to replace that
lost in the filter change, as well as using oil analysis to check the
chemical status of the oil. Tha actual limiting factor in diesel
engine oil is its ability to suspend the carbon particulate. This is
why diesel oil is jet black on a change. This startles new diesel
owners the first time you see it changed... you think the oil is
burned!

In my situation, I change the oil in the Tahoe on a 5,000 mile
interval based on the oil analysis data I obtain on each change. This
gives me information about the carbon particulate in the oil, if there
is any coolant leakage from gaskets, etc. Additionally there is a
metals analysis provided that indicates any unusual wear going on in
the engine such as bearing failure, rings etc.. This is very useful to
avoid a catastrophic engine failure because it allows preventive
maintenance to occur before a failure.

Interesting finding: During a particularly hot summer of 98-100 degree
days, I was towing a very large boat for the Sheriff's office several
times a week between Baton Rouge and New Orleans. I was curious
about   what the analysis would show, because I was operating the 6.5
diesel at thermal limits and had to pay attention to engine temps to
avoid overheating. During this time I found that the engine would
operate happily at 63mph (GPS verified) with normal 190 degree
readings. Moving to 65mph produced an instant engine rise to 210 which
is the fully open thermostat position in the GM.  Attempting to go
over 65 would immediately redline everything.

Oil analysis for that towing setup showed increased particulate
(carbon particles from the diesel blowby) indicating much higher load
on the engine, which is expected, along with higher metal readings
than usual, indicating higher wear on the engine. The lab (Blackstone
Labs at http://www.Blackstone-Labs.com) wrote in its notes that for
heavy tow situations like I was doing, that a less than 5,000 mile
interval was suggested. I.E. Use the 3000 mile heavy tow interval
recommended by GM.

I use the same change interval on the Chrysler for the same reasons.

For anybody operating a turbocharged engine, synthetic is the only way
to go because the most common and expensive failure in such an engine
is the turbocharger bearing failing, necessitating turbocharger
replacement in most instances. This is because a turbocharger
typically will spool up to somewhere in the area of 50-100,000 RPM
under load, and maybe more if passing or climbing a grade with your
foot in the throttle. This creates a lot of heat in the turbo for the
bearings to deal with. Now the problem; you come to a McDonalds or hit
you driveway at home and shut off the engine after a speed run. Engine
stops and the turbo is still running along at very high rpm.  Since
the engine is stopped, the oil pump is off, and there is no oil being
supplied through the turbo bearings for lubrication and cooling.  If
you are running a petroleum oil, the stuff will overheat and "coke".
In other words the oil boils off and burns, leaving a carbon goo in
the bearing surfaces kind of like charcoal that is very abrasive and
damages the bearing. Eventually the bearings will fail in much less
time than normal because of the damage caused. Turbochargers are not
cheap, and even if you know how to do a R&R of the bearings, it is a
pain to fool with doing the repair.

Synthetic oil does not have this probem at all due to its superior
heat survival abilities, so the turbo is fully protected. I might add
that common sense also dictates that after a hard pull, it is
appropriate to let the engine idle about 5 minutes to cool the
transmission and engine to let things come back to normal. I do this
even when cruising on the interstates and drop off for a stop.

Finally; Cost.  The Mobil Delvac-1 that I use is purchased at a local
wholesaler because most retail outlets do not stock the diesel rated
Delvac-1. My case price is $72.00 for 4 gallons. The 6.5 diesel uses 2
gallons per change. You can figure out the per quart cost, which I
dont mind at all. The Mobil-1 5w in my wife's car is available a
Walmart or KMart at just a little more cost than petroleum oils, so is
comepetetive. If I get her oil at my wholesale place, it is a little
cheaper than the discount stores!  There is actually no reason why I
could not use the Delvac-1 oil in the car other than the 1 gallon
bottles happen to be perfect for my 2 gallon engine, and the Chrysler
uses 5.e quarts and would result in a partial bottle of Delvac hanging
around. The quart bottles are convenient for the Chrysler!

Is the synthetic better? Definitely if you keep vehicles as long as I
do... My last Diesel Blazer had 595,900 miles on it without any major
engine wear. If you trde in ever couple of years, probably not. A lot
of diesel owners are quite happy to run Mobil Delvac-1300 or Shell
Rotella-T and love it. Our user group did a survey and found that most
Chevy diesel owners run Rotella-T and use a 3,000 mile interval.

Interesting trivia: The new Corvette HO engine REQUIRES Mobil-1
Synthetic oil ONLY due to its tight tolerances and high operating
temperatures...that should tell you something !  All Turbine jet
engines run full synthetic for the superior characteristics.


Links:

Amsoil information : http://www.amsoil.com/literature.htm

Mobil synthetic data : http://www.amsoil.com/literature.htm

interesting oil additive article (Slick50, Lubrilon etc) : 
http://www.uneaqdesigns.com/civic/others/snakeoil.html

Shell Rotella-T site: http://www.shell-lubricants.com/Trucking/


Hope all this helps !

Doug