Semi and full Synthetic - According
to a service bulletin, Volkswagen recommends the use of synthetic
oil in the TDI engine. Herein lies the dilemma, as if you take
your Volkswagen to a dealer for service, they may try to use
an oil which is not CG-4 rated and isn't really a full synthetic.
There are a limited number of oils on the market in North America
which satisfy the following criteria: CG-4 or CH-4 rating, full
synthetic, viscosity 5w30 or 5w40. These oils are suitable for
VW's full recommended oil change interval and the viscosity
range is suitable for all climates in North America. Contrary
to what dealers may tell you, neither Mobil 1 nor Castrol Syntec
fulfill all of these requirements - and that information is
right on the bottle.
The information in this section refers to API service classes
which are North American standards. Different standards
for engine oils are used in Europe and elsewhere. It should
be noted that since this vehicle was developed in Europe, it
is much easier to determine whether a European engine oil is
suitable. Any synthetic oil meeting the specification VW 505.00
is suitable for use with this engine with the full recommended
oil change interval. The VW 505.00 is the manufacturer's
own specification, but in North America this specification is
rarely seen, so we must rely on the API grades.
Oils which are suitable for the full recommended oil change
interval in all climates include, but aren't limited to:
Mobil Delvac 1, 5w40 (full synthetic, a reformulated version
of Mobil 1 which is intended for diesel engines)
Chevron Delo 400, 5w40 (full synthetic version)
Shell Rotella T (full synthetic version, not to be confused
with Rotella SB synthetic blend or regular Rotella T non-synthetic)
Amsoil Series 3000, 5w30 (full synthetic, CH-4 rated)
Amsoil High Performance, 10w40 (full synthetic, CH-4 rated)
Amsoil semi-synthetic 15w40 (CH-4 rated and high quality,
but almost as expensive as the full synthetic, and higher viscosity
at low temperatures)
Redline, synthetic version (make sure you get the type meant
for diesel engines, with the CG-4 or CH-4 rating)
There are intermediate classes of oils in between full synthetic
oils and conventional oils. These include synthetic blends,
and so-called "Group III" hydroisomerized oils, and
are also available in viscosity ranges suitable for all climates.
They include:
Shell Rotella SB (synthetic blend)
Petro-Canada Duron, various viscosity's (Group III, various
grades available, ensure CG-4 or CH-4 rating on the bottle)
Castrol Syntec 5w30, 5w40 (Group III - note that this oil
is frequently recommended by VW dealers but is NOT rated CG-4
or CH-4, and isn't a full synthetic - which calls into question
what the dealer is telling people ... this forum is generally
of the opinion that Castrol Syntec is not the best choice for
this engine)
In warm weather, a good-quality non-synthetic oil meant for
diesel engines with CG-4 or CH-4 ratings may be used. They're
not suitable in cold weather due to reduced cold-pumping properties,
and it's prudent to shorten the oil change interval because
non-synthetic oils may not resist breakdown at high temperatures
as well as the synthetic oils (remember that turbocharger).
These oils are much easier to find. These include:
Mobil Delvac 1300, 15w40
Shell Rotella T, 15w40
Chevron Delo 400, 15w40
Beware of other brands that claim to be diesel-rated or turbo-rated,
but are actually just plain cheap. Use the good stuff. If you
doubt this, ask transport truck drivers that own their rigs
what they use. Chances are it will be Delvac or Rotella.
In cold weather, if CG-4 or CH-4 rated synthetic oil cannot
be found, regular Mobil 1 rated CF in viscosity grades 0w30,
5w30, or 10w30 may be used, but with a shortened oil change
interval because this oil doesn't have as much capability to
handle soot.
So what's the deal if something else is used besides the
expensive and sometimes hard-to-find 5w40 full-synthetic CH-4
rated oil?
Conventional oils that are meant for diesels are usually
viscosity SAE 15w40. That's okay in warm weather, but not in
cold weather. You want oil to reach that turbocharger as soon
as possible after a cold start, and it takes longer to get there
if the oil won't pump easily. Synthetic oils have many advantages
over conventional oils, not the least of which is better cold
pumping characteristics, and hence the common 5w40 viscosity
grades.
It is possible to get some non-synthetic oils with viscosity's
such as 0w30, 5w50, etc. In non-synthetic oils, these can only
be achieved by heavy use of viscosity-index modifiers, a type
of additive, whereas synthetic oils can easily achieve a viscosity
range like 5w40 with little or no use of viscosity-index modifiers.
For various reasons we'd rather not get into, it's better to
have the viscosity right in the base stock, than to tinker with
the viscosity using additives.
Oils that lack the CG-4 or CH-4 rating don't have the same
level of anti-foaming and soot-dispersing capability. The best
quality diesel-engine oils deal with it and render the soot
as harmless to the engine as possible. Oils that don't meet
the CG-4 or CH-4 ratings can't handle as much soot, so you need
to change them sooner.
Finally, cheaply made oils (not the same as cheaply priced
...) usually won't have the same resistance to breakdown at
high temperatures, that good quality oil does. High temperatures
are found in the turbocharger. When oil breaks down at high
temperature over a period of time, it "cokes" or builds
up deposits in the high-temperature area, which then restrict
lubrication. Bye-bye, turbo. There has been one reported turbo
failure which was traced to lubrication failure. Do a search
of the forums for "turbo failure" to find out what
oil he was using...
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