The oil weight post...

[1Greyteg]

Here is some more interesting information on the topic of oil Viscosity that was taken from an article written by John Wilkinson over at Audiworld. It discusses weights in depth not so much as brands or synthetic as opposed to natural, those topics can be for another posting.

Audi's are some high performance vehicles often dealing with similar complex machinery and of course boost.


"The question of which viscosity grade of motor oil is best for use in
newer Audi engines seems to come up daily in the forums. Herein I will
attempt an answer:

Any 5W-30 motor oil, conventional or synthetic, displaying the
"starburst" API (American Petroleum Institute) certification mark on the
front of the container should be sufficient for all seasons, winter and
summer, even with very hard street driving. That's the short answer,
those not interested in details need read no further. Others, read on.

All metal engine parts need to be separated from each other while
moving in order to prevent friction and wear on the parts. This in done in
modern production engines using a thin film of oil (usually less than
1/10,000 of an inch thick). Oil's viscosity, in part, determines how thick
the oil film will be, and how much friction there will be between those
parts when separated by the oil. Higher viscosity means thicker oil films
and more friction within the oil. Obviously, one wants a viscosity high
enough to prevent parts from grinding against each other, but no higher
than that, because any more results in excessive friction within the oil,
leading to excess heat and power loss. The ideal oil would provide the
minimum required viscosity under all conditions. Unfortunately, oil's
viscosity diminishes with increasing temperature, necessitating the use
of an oil which will have the minimum required viscosity at the highest
expected temperature, and greater than optimal viscosity at lower
temperatures.

The first number, preceding the "W" (for Winter), in an oil's viscosity
grade, is an indication of low-temperature performance -- the lower the
better. The second number represents the oils high-temperature
viscosity, but higher is not always better! One wants to choose the
minimum viscosity that results in an oil film thick enough to prevent wear
at the temperatures one expects to encounter. Only the engineers that
designed the engine know what viscosity is required to provide
adequate film thickness without unnecessary friction, so you're stuck
with their recommendation. For what its worth, I trust the engineers --
Volkswagen warrantees it's engines for 100,000 miles, which means
that it must expect few failures before 100,000 miles, even given most
users tendency to ignore proper break-in, warm-up, oil-drain intervals,
and maintenance procedures. So, if you plan on getting rid of your car
before 100,000 miles, stop reading here. Any conventional 5W-30, as
used by many VW and Audi dealers, will not affect your engine life
before 100,000 miles. People who intend to keep their cars for
200,000 miles or more, like I do, may continue reading.

Older owner's manuals showed a chart indicating that "energy
conserving" 5W-30 was suitable for all temperatures, but a confusing
note indicated that 5W-30 should not be used for "high-speed,
long-distance driving." Beginning with the 2000 model year, manuals
indicate that any conventional or synthetic motor oil may be used as
long as it meets one of the following specifications: ACEA A2 or A3,
VW 500.00 or 505.00, or API SJ. API SJ is the most current API
specification, which, if the oil also meets the most current ILSAC
(International Lubricant Standardization and Approval Committee)
requirements, is always indicated by a "starburst" on the front label. The
manual also notes that 5W-40 is the factory fill oil, and other sources
have indicated that it is a conventional mineral oil, not synthetic. The
manual also states that 5W-30 may be used if 5W-40 is not available.
5W-40 is a viscosity grade most commonly found in Europe, as are the
ACEA specifications. (ACEA stands for Association des Constructeurs
Europiens de l'Automobile -- the Association of European Automotive
Manufacturers, of which Volkswagen is a member.)

There has been some concern expressed among new owners that
5W-40 is not more available in the U.S. An API SJ approved 5W-30
must have a high-temperature/high-shear (HTHS) viscosity of at least
2.9 centiPoise (cP), and most brands, conventional and synthetic, fall
within the range 2.9-3.5 cP. This is lower than the minimum 3.5 cP
required of ACEA A2 and A3 oils, and many have wondered if 5W-30 is
a compromise that they shouldn't be making with their expensive new
cars. (I wondered that myself.) However, it seems likely that Audi
recommends 5W-40 where available, because most places where it is
available tend to allow "high-speed, long distance driving."

"High-speed, long distance driving," by European standards, likely
means several tens of miles at speeds above 100 mph. The power
required to overcome atmospheric drag at 130 mph (most Audi's
governed top-speed) is more than twice that required at 100 mph. The
result of this is that at any average speed of less than 100 mph, your
engine is under only half the load and is probably producing less than
half the heat that Audi felt necessitated a 5W-40 oil. Driving at 75 mph
in an Audi requires only about 25 hp, and does not heavily load the
engine. Your engine is likely more than well protected with an API SJ
5W-30 if you drive mainly on public roads, and do not average speeds
greater than 100 mph over distances greater than a few tens of miles.
Short sprints up to 130, if you are fortunate enough to live where that is
possible, should not cause a problem. Only sustained high-speeds heat
the oil enough to significantly reduce viscosity. Many people have
reported that even at local track events their oil temperature has not
increased dramatically. Therefore, the only conditions which might
require 5W-40 are those which result in prolonged heavy loading of the
engine, such as "high-speed, long-distance driving," or towing a heavy
trailer up the side of a mountain. Given that, it is almost certain that
higher viscosity oils, such as 5W- and 15W-50, are complete wastes of
horsepower, placing undue (though minor) additional strain on your
engine, and raising operating temperatures for no real benefit.

In addition to this reasoning, and Audi's recommendation, I have also
received recommendations for 5W-30 from two synthetic lubricant
manufacturers -- Mobil and Redline. I spoke with real engineers at both
companies, and they were adamant that even for very hard street use in
North America, any viscosity grade higher than 30 would be a waste. All
felt that I would see the best performance in my 1.8T, especially
reduced turbo lag, by using one of their 30 grade oils. Since both
companies market higher viscosity oils (10W-40 and 15W-50), neither
had any apparent reason to attempt to "sell" me on lower viscosity oil,
yet both strongly recommended that I use 30 grade.

Thus far I have written mostly about 5W-30, and ignored other viscosity
grades and the contentious issue of conventional versus synthetic oil.
All 0W-, 5W-, and 10W-30 oils must meet the same 2.9 cP HTHS
viscosity requirement for API SJ certification, and therefore all will
provide ample protection for your engine. The lower winter viscosity
grades will be more valuable in colder climates. 10W generally flows
and pumps well at four degrees below zero on the Fahrenheit scale,
and each grade below that buys you another nine degrees. Synthetic oil
is vastly superior to conventional oil of the same grade in its
low-temperature pumpability, high-temperature stability, long-drain
capability, and high lubricity (low friction). However, all these benefits
may not be apparent in a car used in a temperate climate, with oil
changes at intervals specified by the owners manual. I therefore
cannot say if you will reap enough benefit to recoup the added costs of
changing your oil with synthetic. I live near Boston, and change my oil
with Mobil 1 5W-30 at the required 5,000 mile drain intervals while
under warranty.

As always, YMMV.

On-line references:

1. Lubrication Theory and Practice -- includes information on viscosity
and the additives common to motor oil.
http://www.lubrizol.com/referencelib...eory/index.htm

2. Ready Reference for Lubricant and Fuel Performance -- includes
detailed information on API, ILSAC, and ACEA specifications and test
procedures.
http://www.lubrizol.com/referencelib...ence/index.htm "


Pretty interesting don't you think? Our factory reccommended weight from Honda is: 5W30 BTW.


Good luck & happy oil changing.

A.