Despre lubrifiantii autoturismelor. Pareri, intrebari, raspunsuri, etc.

Cat de des il schimbi? Daca suma este pana in 10.000 km nu are rost sa iti faci procese de constiinta. Baga orice brand de ulei semi-sintetic decent. Daca suma e pana in 15.000, orice brand de ulei full sintetic decent.

...
Cum va explicati preturile ridicol de mici ale lui SHU 5w40? E 90 de ron 4 litri?

Unu' sau mai multi Shell-isti cu o experienta mai mare de 10 schimburi ) sa ma ajute cu producatorul bidonului asta. Eu nu am mai vazut/cumparat asa ceva, e in regula?

In regula pentru ce? Care e mai exact intrebarea? Daca e legit producatorul sau daca e bun pentru masina? In acest caz, ce masina?

Base oil production
Although only 20 % of EU refineries produce base oil, some actually specialise in it.
Figure 1.7 and the associated table (in Chapter 1) identify the refineries specialised in the
production of lubricant and bitumen. More extensive information about the processes can be
found in the general literature (e.g. [ 231, Sequeira 1998 ]).
Purpose and principle
Lubricants are a blend of different grades of base oils and special additives. To produce a
suitable lubricant, certain properties of the base oil are very important: viscosity, viscosity index
(VI: a high VI means that the viscosity changes very little as the temperature changes, and vice
versa), high resistance to oxidation, low pour point and good dope susceptibility or
compatibility.
Base oil is a speciality product and consequently not all crudes are suitable. Heavy crudes are
frequently used as feedstock for conventional base oil complexes. New processes based on
catalytic hydrogenation reactions enable a wider variety of feeds.
Feed and product stream
The feedstocks of a conventional base oil complex are waxy distillate side-streams from
vacuum distillation units (Section 2.19) and the extracts from deasphalting units. Atmospheric
residue feedstock to the vacuum distillation unit consists of various types of hydrocarbon
compounds with different suitability for base oils, e.g.:
 Aliphatic or paraffinic: Normal (n-)paraffins and iso (i-)paraffins form this group. The
n-paraffins have high VI and melting points, and at ambient conditions form crystals,
which must be removed to reduce the pour point of lubricating oils. I-paraffins have
lower melting points, very high VI but lower viscosity.
 Naphthenic: The naphthenic rings lend high viscosity, a low melting point and a good VI
(less than paraffins) to lubricant oils.
 Aromatic: The aromatic rings lend high viscosity and a low melting point to compounds
but a low VI to the oils. For this reason, they are considered the least satisfactory type of
compounds for lubricants. The ratio in which the three groups are present varies from
crude to crude.
New industrial facilities can also use natural gas as a feedstock (gas-to-liquid processes).
The American Petroleum Institute (API) has developed a base oil classification system which
categorises base oils into five major groups, classified on the basis of the following three
criteria:
 The percentage of saturates (the higher the number of saturates, the better the resistance
to breakdown or loss of viscosity).
 The sulphur content (the lower the sulphur content, the better the purity: thus the product
is less corrosive and there is less potential for oxidation).
 Viscosity index (the VI is an indication of the rate of change of viscosity against
temperature, and the higher the VI, the better). The viscosity is the oil resistance to flow
and shear. It is the single most critical physical property of the oil, as it affects both the
wear rate and the fuel efficiency.
The five groups defined by the API are:
 Group I: Contains less than 90 % saturates and/or greater than 0.03 % sulphur and has a
VI between 80 and 120. Demand is around 65 %, with a decreasing trend.
Chapter 2
46 Refining of Mineral Oil and Gas
 Group II: Contains more than 90 % saturates and less than or equal to 0.03 % sulphur and
has a VI from 80 to 120. The demand is around 25 % and tends to go up.
 Group III (known as unconventional base oils - UCBO): Contains more than 90 %
saturates and less than or equal to 0.03 % sulphur and has a VI of more than 120.
Groups III and II oils are made by the same process, but for group III, the VI is increased
by higher temperature in the hydrocracker or by appropriate crude selection as a
feedstock. Group III advantages over group I and II base oils are that it is more fuelefficient,
has longer drain intervals, is environmentally friendly and is engine-protective.
Demand is around 10 % with a growing trend.
 Group IV: Synthetic base oils.
 Group V: All other base oils.