<VV> Synthetics Oil GM Engineer's Opinion (long)

[John Dozsa]

The following is the response of a GM engine development engineer to a
motorcycle forum on extended mileage oil changes.  The link to the forum
was posted on VV months ago.  I found it so interesting I saved a copy. 
Read with an open mind and form your own opinion about your favorite oil
and oil change habits.  Only the GM engineer's responses to questions,
converted to plain text format, are included.  The GM engineers
experience and credentials are in the first few sentences of the last
paragraph.  It's taken special handling to get this long message posted,
thanks to vv-help.  I've got the entire original in pdf format for those
interested.

John Dozsa


Keep in mind that there are a lot of reasons to change the oil. Oil
oxidizes with time and temperature, oil gets contaminated with
combustion byproducts, oil gets contaminted with soot from blowby, oil
gets contaminated with fuel and water...particularily during cold
starts, acids form in the oil, oil gets contaminted with dust/dirt/
debris, the antiwear additive in the oil (the "zinc" or ZDP) gets
depleted with engine revolutions, the antioxidants/
anti-acids/detergents/dispesant additive deplete with time and engine
revolutions.

Synthetic oil addresses the oxidation as it will handle higher
temperatures but that is about the only advantage of synthetic...so...in
short, using synthetic does NOTHING to allow a longer drain interval.
Synthetic has the same amounts of ZDP, same problem with fuel and water
contamination, same problems with other contaminates including soot,
same problem with acid buildup, etc.... All reasons why synthetic oil
does NOT allow longer drain intervals. The water from combustion
byproducts/blowby combines with the sulfur in the fuel in blowby to form
sulfuric acid over time so oil acidity slowly increases with time and
miles and synthetic oil does nothing different to prevent this. You have
to change the oil before the anti-acids in the oil additive package are
overwhelmed. If oxidation were the only reason to change the oil then
synthetics would have an advantage in terms of life or extending the
drain intervals. Unfortunately, oxidation due to temperature is RARELY
the determining factor for the drain interval so any advantage
synthetics might have in this area are moot. I would recommend sticking
to the recommended drain intervals even if you use synthetic oil.

It is interesting that the new Mobil 1 "extended service" oils added
more ZDP to the oil to prevent depletion of the anti-wear additive to
market the extended drain intervals to 15,000. BUT....read the bottle.
It specifically states that if your engine is under warranty, change the
oil at the specified intervals...hmmm....so much for their "guaranteed
15,000 mile interval. Another gem on the bottle is the statement that
"if your engine has an oil life monitor follow the oil life monitor and
do not use the extended drain interval." The bottle also says that the
extended service is void if the engine operates in heavy
duty/commercial/livery service, is idled a lot or is operated in a dusty
environment. That pretty much eliminates a LOT of other applications and
matches the manufacturer's recommendations for sooner oil changes under
those conditions. So..after reading the can, exactly what good is the
"extended service" Mobil 1. In addition, if youlook carefully, the
extended service Mobil 1 does not have the API SG3/SG4 rating as it
exceeds the antiwear (zinc) concentration for the API SG3/SG4 ratings.
This is not necessarily bad for motorcycles but makes the oil a
NON-recommended oil for most modern passenger car applications. I am not
making this up....read the fine print on the bottle yourself. I would
change the oil at the normal intervals even if you do use a synthetic
oil.

It isn't MY conclusion...it is a fact. Mobil even says the same thing.
They have not stated anything about extended drain intervals with their
products until the recent addition of the "extended service -15000"
synthetic oil. And they had to modify their existing Mobil 1 product to
make that claim (modified to the extent that it doesn't conform to the
SG3/SG4 specs anymore) and they STILL put tons of qualifiers on the
15000 claim with the disclaimer about changing it according to the
manufacturer's oil life monitor, and changing it sooner if under
warranty or operating in towing/commercial service or dusty
environments. I am not making that up....read the bottle for yourself.
With all the other reasons for changing the oil there is no way that
synthetic can claim a longer drain interval. I worked extensively with
the GM Research oil chemists that developed the GM Oil Life Monitor and
know for a fact that it doesn't change anything in the model for cars
with synthetic oil from the factory. I agree that it is possible, under
certain conditions, to run the oil past 15,000 or even 20,000 miles in
passenger cars with the oil not being "used up" or "worn
out"...but...that is assuming no safety factor at all in the oil life
and it is under the best of conditions. And...the testing that proved
this was NOT synthetic. If the oil is being used under conditions that
allow an extremely long change interval then conventional oil will last
just as long as synthetic under those conditions. The single advantage
of synthetic is it's ability to operate at temps above 305 F without
oxidizing rapidly. Since there are few applications where the oil gets
that hot the advantage is moot and contributes zero to extended drain
capability. Even my CBX with a partial fairing blocking part of the
engine never gets the oil to 300 even running on the freeway at 80 in
summer weather...I've checked. The fact is that the "extended service"
claim for the Mobil 1 15000 oil is a bit hollow...especially when they
add several $$$ per quart for the 15000 oil. A modern Cadillac Northstar
or LS1 engine will go 12500 miles on the oil life monitor if used in
highway driving, best case conditions...and that is validated with
conventional, non-synthetic oil !!! So for the extra $$$ for synthetic
and extra $$$ for 15000 you only get 2500 extra miles...and Mobil tells
you on the bottle NOT to ge 15000 if your car has an oil life monitor.
If you saw data showing the oil was fine with extended drain intervals
then conventional oil would have done the same thing on that particular
test. Forget the idea that synthetic allows longer drain intervals. It
is hype by some of the synthetic marketers (primarily Amsoil) to
sell/justify their expensive (highly profitable) product. They test
under one set of best case conditions and then imply that that is the
case for all conditions.

The other thing to keep in mind with oil drain intervals is that
different engines have distinctly different oil lifes. The life of the
oil in the engine is VERY dependent on the engine design, features in
the engine and what is expected of the oil. As an example from the
engines that I work on, the 93-99 Northstar engine would have a maximum
oil life of 7500 miles. This was bumped up to 12,500 miles with the
redesign of the engine in 2000 model year. This is the maximum oil life
under optimum operating conditions, not the recommended change interval
all the time. The difference in the engines is that the 2000 engine has
rolling element cam followers instead of direct acting lifters. The
rubbing element or direct acting lifters take the antiwear ZDP out of
the oil much faster and the direct acting tappets are far more dependent
on oil quality and the presence of the ZDP to live. Oil that would be
depleted of ZDP in the earlier engines in 7500 miles is still
serviceable at 12,500 miles in the newer engines. Older passenger car
engines had rubbing element lifters, rubbing element rocker arms,
pushrod tips, distributor gears that drove the oil pump, spur gear oil
pumps, etc... Those engines needed a lot of antiwear protection and used
it up quickly. 3000 mile oil changes on those engines with the oils of
the day were probably stretching it under some conditions. Modern
engines have gerotor oil pumps, no distributor gears, rolling element
everything in the valve gear....they do not chew up the oil nor need
high levels of anti-wear additives. Plus, the improved PCV systems keep
the oil cleaner. Any oil claims of extended drain intervals that do not
make the distinction of what type of service or what type of engine
should be highly suspect and considered primarily a marketing ploy.
Period. Motorcycle engines, like the FJR, still have rubbing element,
direct acting tappets that need lots of ZDP and take the ZDP out of the
oil fairly quickly. Synthetic has no advantage nor makes any difference
in this respect. In addition, the oil lubricates the gear box where the
gear mesh shears down the oil viscosity and takes even more ZDP out of
the oil. Wet clutch action contaminates the oil also and is another
source of ZDP depletion. Since the basic model for oil life involves the
linear depletion of ZDP in the oil due to metal-to-metal contact at
lifter interfaces, gear interfaces, etc. I would guess that a motorcycle
engine degrades oil life much more rapidly than a car engine...probably
twice as fast. Also, motorcycle engines turn twice the RPM of car
engines for any given maneuver so that multiplies the oil degradation by
2. The oil life algorithms (that have proven to accurately model engine
oil life beyond a shadow of a doubt) actually count engine revolutions
to establish the basic oil decay rate...so...the more revolutions the
greater the degradation. This linear decay rate is multiplied by various
factors that account for the oil operating temperature, ambient
conditions, soak times, run times, engine load and many others. Short
trips in cold weather will add considerable deterioration because of the
effects of contamination by gas and water. Since cold weather operation
is not much of a factor with bikes and they do tend to get thoroughly
warmed up each ride (most people don't "housewife" a bike on short trips
and many stops) I would guess that the main factor in oil life with
bikes is the depeletion of the antiwear additives....which would be the
same with synthetics or conventional oil. Understand, also, that any
modern oil that meets the SL or SM API performance requirements have
quite a bit of synthetic content in them. Any multivis oil that meets SM
performance specs must have a synthetic polymer Viscosity Improver
package or it wouldn't pass. So, any modern oil is a synthetic "blend"
as some companies like to market and charge extra for....LOL.
Amsoil.....????.....That is an oil marketing company that utilizes a
pyramid scheme to sell their product thru a system of distributors and
dealers and such. They know absolutely nothing more about oil than Mobil
or Texaco or the other major oil manufacturers. Their bogus claims are
meant to sell their products at high prices to benefit their pyramid
marketing scheme. How could they justify the high price they charge for
their product otherwise. Their products probably perform well to some
extent but they have no outstanding attributes that others do not have
for half the cost. Their claims of long change intervals are completely
nonsense. They base them on the lower oxidation rates of their synthetic
products at high operating temps. As mentioned, that is rarely, if ever,
the defining factor in oil changes and the testing that determines the
oxidation rates is run at temps above what most engines will ever
operate at. They take something completely out of context and pretend
that it is a big advantage. It isn't. If you look at all the tests that
oils must pass to meet the API standards for performance, Amsoil only
quotes selected results in areas of testing that do not replicate normal
engine operation. If you really understand ALL the things that govern
oil life Amsoil's claims evaporate. They make themselves sound very
technical and quote lots of "data" but it is a smokescreen to cover
their marketing scheme that benefits their distributors and dealers.....

First, though, let me be clear. Synthetics, such as Mibil 1, are
excellent products. They can survive at temperatures well above the
oxidation limits of conventional oil of 305 F. If an engine operates at
those oil temperatures then synthetic is applicable. Synthetic offers
good low temperature viscosity and pour points... low meaning below -40.
Down to the -30/-40 range conventional oils are fine. If you are
searching for oil on the northslope and cold start regularily at -40
then consider synthetic. Other than that, synthetic oil's usefulness is
questionable in passenger cars. Racing teams use synthetic oil for
several reasons. First and foremost is marketing. If it is "good for
racing" then it must be great stuff, right??? Fooled you , didn't
it..!!! LOL LOL The racing teams get paid lots of sponsorship $$$$ to
run the oils and put the stickers on the cars. That is why they use it.
If someone paid them enougth money to run lard in the motors they
probably would. The engines will run fine with conventional oils as
evidenced by teams sponsored by conventional oil companies that do not
run synthetic. In racing things happen to often drive the oil temps
above 305 F. If this happens....the synthetic can take it and
conventional oil would have a limited life. It lets the NASCAR boys tape
over the oil cooler for better aero during qualifying and if the oil
creeps to 350 in the process there is no harm done. So it has a marginal
use and is a good insurance policy for when the going gets rough and
that fender gets pushed in an blocks off the oil cooler. There are a
number of new cars that specify Mobil 1. I work specifically on several
of them. The Corvette LS1 is spec'ed a synthetic oil engine and the RWD
Northstar engines in the SRX/STS/XLR are also factory filled with Mobil
1. So will be the supercharged Northstar in the STS-V/XLR-V. Why you
ask?? One simple reason. There is no need to put an oil cooler on the
car if it has synthetic oil in it. If the owner takes it to a track day
and runs the car on the track hard the oil will get over 305 without an
oil cooler. Synthetic oil will take it and conventional oil would be
questionable. Otherwise, the performance cars like this would all need
large oil coolers and all the associated plumbing. Putting all that
extra equipment on all cars so that the 2% that actuallly see the track
will keep the oil cool is not a good idea. Better to leave off the
cooler (less expense, less chance of oil leaks, less complexity, less to
maintain with age) and protect the small percentage of engines that
might get the oil above 305 with the synthetic. Regardless of what you
have read, were told or believe this is the main reason that factory
cars are spec'd for synthetic. Period. I know because I work with them
everyday and can assure you that that is the truth. Interestingly, the
real hotrods, like the STS-V run oil coolers AND synthetics because the
engine will push the oil temp over 305 even with a large cooler if used
for continuous track work. So, even though the car has an oil cooler,
the same logic and reasoning applies...use the synthetic to keep from
having to put a HUGE oil cooler on it. The engine oil temp does not run
any cooler with the synthetic, by the way. I have run lots of engine
cooling tests with conventional and synthetic oils and the oil temp is
the same regardless...just that the synthetic has highe oxidation temps.
If an engine is designated for factory fill with synthetic it has other
uses as well. In the case of the Northstar engines in the STS/SRX/XLR
the engine has variable valve/cam timing (VVT) on all four cams. The VVT
system uses engine oil pressure as a hydraulic system to move the cam
phasers using control signals from the PCM. The VVT system is a
hydraulic circuit that is separate from the normal engine lube circuits.
In cold start situations the viscosity of the "hydraulic oil" must reace
a certain level before the VVT system will respond quickly enough to
allow it to be used. The more linear cold viscosity of the synthetic
products allow earlier application of the VVT on cold starts. Without
the synthetic the system would still work fine...just the cam phasers
would "park" until the engine oil reache a certain temperature. Since
the synthetic was spec'd anyway, it is exploited in the engine design to
be able to better utilize the VVT system. So.....that is why factory
cars have synthetic. Not because it is magic or has better "wear"
properties...just because it can live above 305 for extended periods of
time. Interestingly, the synthetic only adds about 25 degrees of
increased oil temp range above 305. The metal parts in the engine, that
are much hotter than the oil and that are cooled by the oil, cannot take
much higher temperatures. Aluminum starts to loose strength and gets
"soft" enough that it will start to collapse in structural areas. Even
hardened steel , like tappet faces, start to temper and soften at temps
approaching 375/400F so if the oil is starting to approach 330 or so the
tappet faces are getting periously close to the range that they will be
starting to temper and anneal. Not desireable. In a race engine that
will be torn down after the race and wear parts replaced this is not
such a stringent condition but in a passenger car or street bike engine
those temps cannot be seen without damage.....so.....the high temp
capability of the synthetic oil cannot really be exploited by much. As
an aside, you will find that "racing" has little to do with passenger
cars or street bike engines. Just because something works on racing cars
or is used by racing teams does not mean it is good or applicable to
everyday use on the street. The marketers like to make you THINK that
racing means good but that is just marketing and an image. Look at the
facts, first.

Like I said, the synthetics are excellent products. You certainly are
not going to hurt anything using them... Just be aware that in most all
conventional engines in cars and street bikes the use of synthetics is
just not required. The areas that synthetics are "better" is far outside
the normal operating range of the oil so that area or advantage is just
not used nor needed. My main reason for posting on this thread was not
to run down synthetics at all...just make sure that people understand
that the idea of extended drain intervals with synthetics is not really
true and not something that they should be fooled into believeing.
"Extended" means a lot of different things to different people. If
someone reads Amsoils BS and thinks that they can run their FJR 25K
between oil changes they are being sadly mislead. In explaining why
synthetics do not necessarily provide addtional service life it is hard
to not touch on their limitations and compare them to conventional oil.
The data that I see indicates that, under normal use, conventional oil
functions perfectly well. When I see an engine run for 300 hours at full
throttle/max load on an engine dyno with conventional oil and then at
teardown the bearings are not even touched and other wear surfaces are
fine it is hard to understand just how much "better" synthetic oil could
have run....LOL LOL I have seen LOTS and LOTS of engines run like this
and somehow, miraclously, the engines always look fine with conventional
oil. And we don't even add Lucas or Slick50 or ZMax or ???? LOL LOL If
you are using synthetic oil, what gain or advantage do you expect...???
I understand the idea of putting the "best" into something and if you
want to use synthetic I have absolutely no problem with it....just don't
expect miracles and realize that the likely hood of really exploiting
the advantages of the synthetic product in a street engine is pretty
slim. The proper application of synthetic lube products (in things like
the VI package in conventional oil) is already being used and in the
bottle of every oil you buy so the chemists that really understand the
advantage of synthetic products are putting it in the correct
applications for you.

Yea, I agree, oil in turbocharged applications is a good candidate for
synthetic. I have an air cooled backup generator for our house that we
need occasionally....it gets 20W50 Mobil 1 because it will run so hot on
summer days when needed. Good place for synthetic and utilizes the
advantages of it. In very cold weather, there is less viscosity increase
with synthetic. It will improve cranking speeds. Is it needed to help
the engine down to -40....no....but it will make them easier to crank
over. Like I said, I am not in any way running down synthetics...just
want to make sure no one thinks that there are huge advantages to them
unless they are operating the engine in a regime that forces the oil to
very high or very low temperatures. The main thing that I always hate is
the belief that synthetics allow much longer change intervals....a
belief kept alive by Amsoil and their BS. The current engine oils for
gasoline engines (rated GF3 or GF4 in the starburst symbol) contain
synthetic friction modifiers that improve fuel economy. That is in all
oils sold as "gasoline engine" oils and are the things that you want to
avoid in your wet-clutch bike. Some of the "fuel economy" attributes of
the oils get mixed up in the addition of the friction modifiers. A
synthetic will typically be a slightly lighter weight base oil due to
the flatter viscosity curve as the temperature of the oil changes.
Thinner oil will always be better for fuel economy (within reason....as
long as it is not so thin that metal to metal contact occurs due to
lower film thicknesses) which is why manufacturer's specs went from
10W30 to 5W30 and to 0W30 in some applications.

I am a newbie to this site...LOL...but not a newbie. 33 years at GM and
counting....the last 20 in engine development. If you want to see what
I've been working on the last few years score the May issue of Hotrod
Magazine and read the article on the Supercharged Northstar for the
STS-V/XLR-V. Class 8 , over-the-road diesels can go for long distances
without oil changes simply because they carry a LOT of oil onboard. My
brother's White/Detroit Desiel had over 20 gallons on board. So....each
particle of oil doesn't spend nearly the same amount of time in the
engine compared to car or bike engines that only carry 4 or 5 quarts.
Since the engine has 15 times as much oil on board it can go 15 times
further on a drain interval all other things being equal. So if a car
engine can go 12,500 miles (best case) a truck could go nearly 200,000
just due to the extra volume of oil. This is a very very simplistic
analysis and assume the truck engine beats up the oil the same as a car
engine..which it doesn't, it is worse..... so take it with a grain of
salt but it serves to illustrate why the longer change intervals are
possible with the trucks. Several other things help. Oil coolers. Due to
the heavy loads and considerable time spent at heavy throttle pulling
hills and such over-the-road trucks have large oil coolers that keep the
oil well below 300 even in the worst climates and steepest grades. Most
of the diesels like that also use bypass filtration. They use a
conventional filter that filters down to say, 20 microns, that all the
oil goes thru each pass. Then, there is a smaller, 2 or 3 micron filter
that only a portion of the oil goes thru. The idea is that eventually
all the oil will go thru the bypass filter and catch the finest
particles. So, keeping the oil cool, cleaning it thoroughtly and running
LOTS of oil in the sytem allow for some long drain intervals. They don't
just run the oil for longer distances without making other provisions.
ZDP is a compound with Zinc and Phospates in it. It is an excellent
anti-wear additive. Trouble with ZDP and gasoline engines is that it
takes out the catalytic converter. Any oil the engine burns passes the
zinc and phophates into the exhaust and both will contaminate and poison
the cat. So....the whole emission compliance of gasoline engines depends
on the catalytic converter so protecting it is primary.. That is why ZDP
is minimized in gasoline engine oils and the drive is to push the
concentrations even lower. That is why modern gas engines have features
that I mentioned (like roller followers, roller rocker arms, no spur
gears, no distributor gears, etc..) that do not require much anti-wear
protection (the hydro-dynamic bearing film formed by the oil is adequate
for those devices) and thus do not deplete the anti-wear additives in
the oil. Want ZDP...???....go to a GM parts counter and buy a can of GM
Engine Oil Supplement (EOS). It is straight 40 weight oil highly
fortified with ZDP. EOS has about 10 times the ZDP of normal engine oil
so it is an excellent additive to "spike" the oil with ZDP for breakin
or to avoid further wear in a marginal lube situation. ZDP is expensive
and has to be blended into the oil with heat so it isn't something that
can just be eyedroppered into the oil. But you can use an oil that is
high in ZDP (like EOS) to spike the oil in the crankcase. BTW...you
don't get any ZDP in any of the aftermarket snakeoil additives. Too much
ZDP can also play havoc with wet clutches so there is a balance as to
how much you want in the oil. Diesels have alsways been very hard on oil
due to the high pressures and temperatures in the ring belt area (due to
the high compression and high pressures when combustion commences) and
the fact that most all diesels are turbocharged and the turbos have oil
cooled/lubed bearings. The high heat of the turbo really cooks the oil
and the high ring belt temperatures and pressures will coke a lot of
lube products severely. Multi-vis oils, when they first came along, had
rather poor quality polymers for the VI package. Those VI packages would
cook in the diesels ring belt area and stick the rings. Especially bad
were the multivis oils of the mid 70's and early 80's that were SE and
SF rated. In that time frame there were NO multivis diesel
oils...everything that was approved for serious diesel use by Cat,
Cummins, JD, etc. were all straight weight oils because of the poor
quality of the available VI polymers. Interesting aside....more
Oldsmobile diesels were killed by SE and SF grade 10W40 motor oil than
anything else. Period. Those 10W40 oils were the "hot setup" and the
"most expensive" so people bought them and put them in the Olds diesel
even though the multivis oils were specifically NOT recommended ....
ESPECIALLY 10W40 that has a great deal of VI in it to make the wide
transition from 10 to 40. I stuck the rings in my XS1100 using 10W40 oil
for the same reason because I didn't know any better back in 1980...LOL
Started to use oil bad...pulled the jug off.... the rings were stuck in
the grooves and wouldn't even pop out when the piston was sitting there
in the open. SE/SF 10W40 was the pits and lead to the higher temperature
requirements spec'd for SJ/SL/SM rated oils. Why the long
story...???....Look at Rotella/Delo/Delvac oils. They are multi-vis
(15W40 most commonly) AND they meet every diesel spec for NA diesels,
Supercharged and Turbocharged diesels. They are excellent oils. They
have to be to meet the SL and all the diesel specs and be multi-vis at
the same time. Note that they do NOT meet the SG3/ SG4 requirements
since they do not have the friction modifiers in them for fuel economy.