History of Oil (part 1)

ok - it's a bit quiet, so - here goes ...

HISTORY OF ENGINE OIL Part One

Black and Slippery



Engine oil is slippery, it gets dirty, it drips on the garage floor,
it often appears out of the exhaust pipe as black smoke, it is not welcome
in the kitchen. Even non-drivers know that its presence has to be checked
now and again, with dire consequences if it is forgotten. Oil is thought of
as the life blood of the engine. We certainly know that without it, our
engine becomes a heavy lump of scrap iron. But what exactly is engine oil?
Is there any difference between supermarket GT-LeMans-F1 Supermulti-grade at
£3.00 for 5 litres and Red Line® Race Oil at £15.00 for 1 litre? Are either
of these suitable for my car engine? So much money is spent advertising
certain brands of oil, they surely must be better?



We will examine the development of engine lubrication to attempt to
discover if what we need for our car engine is actually what we are getting.



Very shortly after the wheel was invented, it was discovered that a
smear of cooked animal fat on the axle made pushing a whole lot easier. But,
which was better - roast deer fat or boiled pig? Tests were run -
lubrication technology was born! Vegetable oils were also used in early
times for lubrication, heating and lighting, but the lucky few were those
who lived near the black gold deposits - crude oil. Mankind has been using
mineral oil for thousands of years, but only in the last two hundred has it
been so widely exploited.



Early cars naturally used the slippery by-products of crude oil from
which their fuel was obtained to protect the sliding and rotating metal
parts of the early internal combustion engines. Adjacent moving metal parts
require an oil film between them to prevent seizure and as speed increases,
a medium to carry away heat. Originally, each new vehicle designer had his
own method and type of fuel, lubrication and control layout, as well as
number of wheels and engine size. However as automobile numbers grew,
standardisation set in. A brand new manufacturing industry was born, not
just in the building of vehicles, but in support of the automobile: oil and
petrol in particular were consumables that were soon to be in demand in
every corner of the world. By the early nineteen thirties, the vehicle
manufacturers had recognised that there was a need for fixed standards of
performance of lubricants and fuel so that cars and lorries could be sold
anywhere world-wide, without major modifications or embarrassing failures.
Prior to that, you took with you what you needed.



The Society of Automobile Engineers in the USA took on the task of
setting the standards for engine oil. They made the decision to compare and
define lubricating oils by viscosity. Viscosity, in lay terms, is how easily
a liquid pours. Now this also reflects on the internal shear strength of the
liquid, so for light mineral oils we can state categorically that the higher
the viscosity of the oil, then the stronger it is. Your engine rattles? Put
some thicker oil in it!



The SAE decided to compare the viscosity of oils at 100 degrees
centigrade, albeit they were originally working in Fahrenheit. This is
around the temperature of oil in a big end bearing - the most highly
stressed part of an ordinary car engine. Viscosity decreases with
temperature increase and at around 100oC, mineral oils start to become very
thin and thus weak. Tests at this temperature are thus a useful oil strength
indicator. Viscosity is measured by the remarkably accurate method of
pouring oil through a known size hole and measuring how long it takes to
come out. The result of this is known as kinematic viscosity. Units of this
measurement are mm2/second, or, after the chap who pioneered viscosity
measurement, centi-Stokes (cSt). The SAE then set down numbers to define
ranges of viscosities, as shown in table (1) below.





Table 1 SAE Kinematic Viscosity of Engine Oil





Viscosity @ 100oC

cSt
SAE Rating

16.3 - 21.9
50

12.5 - 16.3
40

9.3 - 12.5
30

5.6 - 9.3
20

less than 5.6
10






This system worked very well and is still in use today. SAE 30 became
accepted as the standard for engine oil, giving reasonable film strength for
the white metal bearings of the day. This weight oil was usable down to
around minus 10o centigrade before it became too thick to move round the
engine, which covered use in the majority of situations around the world.
Lighter and heavier weight oils were available for extreme climate use.
Racing engines, needing a greater film strength due to higher bearing loads,
generally called for the 40 and 50 weight oils.



During the war, engine development was accelerated, with far higher
engine speeds and bearing loads being introduced by advances in aeroplane
engine technology. This was reflected in post war car engines: standard
saloon car engines having the capability of providing pre-war racing engine
power outputs. However higher film strengths and therefore heavier weight
oils were necessary. Unfortunately the SAE 50 weight oil needed in these
engines when hot, has thickened sufficiently by zero centigrade to prevent
an engine being cranked. Engine oils needed to be changed from summer to
winter, with the attendant problems of variable weather conditions and
climates where both extremes were found daily.



Long chain viscosity modifying polymers came to the rescue. The
plastics industry was developing from petro-chemical research carried out
during the war years. One of the discoveries made was the capability of
manufacturing long chain hydrocarbon molecules or polymers. Properties of
some these polymers included the capability of thickening engine oil at high
temperature, without affecting the viscosity at lower temperatures. An SAE
30 weight oil can thus be transformed into an SAE 50 by means of a simple
additive package, without affecting the lower temperature usability.



To differentiate between 'straight' oils and those which had viscosity
modifiers added, the winter or 'w' rating test was introduced. Oils were
originally tested by the floating of a needle on the surface of oil in an
open vessel. The oil was cooled in 5 degree centigrade increments until
there was no movement of the needle when the vessel was tipped. The oil was
then rated as to be usable at the previous higher temperature. Although
today's testing is slightly more sophisticated, the results are the same,
leading to oils being classified for cold temperature use from the table (2)
below.





Table 2 SAE Winter Rating of Engine Oil



Low temperature rating
Temperature at which

oil is usable

25w
-5oC

20w
-10oC

15w
-15oC

10w
-20oC

5w
-25oC

0w
-30oC and below






Straight SAE 30 oil tested in such a fashion shows it is useable down
to minus 10 degrees, thus this oil can be called an SAE 20w30. By adding
viscosity modifiers to thicken the oil to an SAE 50 viscosity at high
temperature then the oil becomes an SAE 20w50. A 50 weight oil, only good
for operation at 0 centigrade, can be called an SAE 30w50. Two oils, both
SAE 50, identical under the old definition, are thus now easily
distinguishable. This became the world wide accepted commercial method of
identifying engine oils. To the benefit of both the oil producers and the
motorist, the pre-war standard SAE 30 was converted by means of an easy
additive into the beloved 20w50.



Technically, it is not acceptable to look at the cold weather
performance of an oil and its 100 degree SAE rating and guess from this what
the performance might be like at other temperatures. For that reason
kinematic viscosity is also measured at 40oC and the Viscosity Index
calculated: the rate of change of viscosity with temperature. For oils of
similar SAE rating, the higher the viscosity index the smaller the effect of
temperature on its kinematic viscosity. This is particularly important when
looking at lubricants for racing, high performance engines and those where
high temperatures and loads are expected, particularly as it indicates how
the oil will perform above 100oC. The Viscosity Index number for engine oil
is not normally quoted on oil cans, for obvious reasons on certain oils, but
is available from all genuine performance oil producers.



Advances in the 1950s and 60s in the petro-chemical industry also led
to comprehensive synthetic detergent packages for oil, and very efficient
anti-wear and anti-scuff additives. Combined with advances in filtration
technology, the motor car engine in the late 1960s had never been better
protected. However, it was needed! With the opening of high speed motorways
around the world and metallurgy and manufacturing technology advances
allowing higher revving and greater specific power outputs from engines,
lubricants were still being challenged. Long chain viscosity modifiers and
detergents are soon destroyed in high load conditions and the oil then
reverts to its original lower viscosity grade. Fossil oils deteriorate with
age, use and mixing with fuel residues, losing over a period of time their
lubrication and protective properties. Mineral oils therefore need to be
changed on a very regular basis. Vehicle manufacturers, on the other hand,
want to cut down service intervals to make ownership as cheap and easy as
possible. In addition, there is the requirement for as light an oil as
possible to cut down friction losses, making the vehicle both quicker and
more fuel efficient. Lighter mineral oils, under more stress, break down far
more quickly.



Help came from the aircraft industry. Gas turbine engines had
developed to the stage where the immense pressures and temperatures involved
would fry mineral oils on contact. The stage was set for totally synthetic
lubricants to enter the automobile market.