Tricky

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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.

Tricky

HISTORY OF ENGINE OIL Part Two
Requirement for stronger oil

We looked in the previous article at mineral lubricating oils, by-products of crude oil used for fuel extraction for internal combustion engines. These became adopted for use as lubricants for these engines, from the earliest motoring days at the end of the last century. We examined the standardisation of engine lubricants in the nineteen thirties by the Society of Automobile Engineers in the USA, how they were classified by viscosity and, on the advent of viscosity modifiers, how the winter rating for engine oil was introduced. This took us up to the nineteen sixties, when passenger car production boomed, world-wide, as second world war production problems and the Suez fuel shortage crisis vanished into the history books.

Mineral oil blenders had always striven to keep up with the increased loading and temperature demands of higher performance engines, introducing higher viscosity lubricants for greater film strength. However, the engine manufacturers always called out for lighter weight oils for performance and fuel economy. In a true case of racing improving the breed, developments from high performance race engines continually breed the next generation road car engines. Lubrication development in the race engine field similarly finds its way to the high street shelves. In the late sixties the first major change in internal combustion engine lubrication was brewing. To see its birth we have to look back a further twenty years.

Two fields of development of interest to us had opened up during the last world war, when the pace of technological development was accelerated by need for survival. The now enormous plastics or petrochemical industry grew from here. This industry was founded, arguably, in the first plant to produce isopropyl alcohol from propylene, in 1921 - a significant step forward for mankind! The underlying principle behind the whole of the industry is to take a cheap and cheerful organic base material, the sector in which crude oil and its derivatives once lay, and add value by the chemical addition of other inexpensive molecular groups such as HOCl, H2O and O2. This has led to the discovery of many weird and wonderful substances, undreamed of seventy years ago, but now filling our life. Pause for a moment and look around: you are surrounded by plastic! Forced by rising oil prices and the pressure of fuel producers to convert more of the available crude oil to energy producing purposes, the plastics industry looked at alternative sources of raw material. Syn gas is a mixture of carbon monoxide and methane, derived from 'natural gas' normally found above oil deposits, but naturally occurring in marsh land and waste tips, apart from the rear end of cows, and was usually burnt off as a nuisance. Historical pictures of early oil rigs display flaming towers of natural gas in disposal. In this more economic and environmentally aware age it is carefully collected and used for household consumption, conversion to bottled gas or as raw material to make ethane and methane, inputs for the plastics industry. Ironically, now methanol production from plant matter is economically viable, once quoted as the bane of a wasteful consumer society, plastics are becoming not only fully biodegradable, but being manufactured using replenishable energy and raw material stocks.

The other factor which affects now the oil we put in our engines was the invention of the turbine engine. From the earliest days of the steam turbine to the phenomenal speed of development of the gas turbine, rotational speeds and thrust loadings beyond the wildest dreams of automobile engine designers were being experienced. The combination of these with the tremendous temperatures experienced by gas turbines mean operating envelopes for lubricants far outside those possible by mineral oils. Because of the exclusive nature of turbines: the small number and high cost price compared to automotive power units turned out by the million, specialist lubricants, immensely strong but frighteningly expensive, were able to be developed. These lubricants borrowed technology straight from the plastics industry.

Originally developed as an exercise to obtain useable fuel from oil shale and coal slack, the Mobil Process, originated by the oil company of that name, produces a family of plastics known as Poly Alfa Olefins, or PAO. These are the basestocks for the majority of our synthetic oils today. Their first use was in steam turbines, but, in possibly the first ever use of synthetic oil in automobile engines, saw use during the second world war in tank engines. In the African desert, where enormously stressed Sherman tanks, using standard Chrysler car engines were frying their engine oil and seizing engines solid, these special lubricants were tried out very successfully. Did Montgomery owe his success to synthetic oil? Was Rommel aware of this?

Post war, use of this expensive product was restricted to turbines and prime-mover low speed diesels, where extreme bearing loadings were found. Competition departments of oil companies were soon quick to discover this wondrously lightweight lubricant that was so strong. It made its competition debut as a gear oil, first as an additive and then as a basestock for the oil. Gear tooth loadings far exceed the scuff of cam followers or big end impact loadings and so require far stronger, and thus, as we saw in the first article, more viscous oils. Reducing gearbox and differential oil drag is a very important contributor to extra performance and heat reduction.

In 1967, the year of Sergeant Pepper and San Francisco becoming famous for its flowers, a new Formula 1 engine appeared. This engine, funded by Ford and designed by Cosworth, was based around a 1500cc Ford Kent block with a 4 valve per cylinder, chain driven double overhead camshaft cylinder head. It was known as the Four Valve engine (FV, leading to the FVA, FVB etc.) This should not be confused with a similar design by Keith Duckworth with belt driven camshafts - the Belt Driven (BD, leading to BDA, BDB etc.) or indeed the 2 valve per cylinder chain driven cams Lotus cylinder head - all fitting the same block. Two FV engines glued together in vee formation by means of a magnesium block casting became the Double Four Valve or DFV. This was the mother, or perhaps even grandmother of the current generation of Formula 1 engines. The DFV engine revved very high. It needed an oil that would not break down at these revolutions and it needed oil additives that were not going to fall apart at these high speeds.

Long chain polymers such as oil viscosity modifiers have a tendency to straighten out whilst under load in a rotating bearing. The viscosity of oil actually in the bearing, at that time, is thus lower than the value of the oil when tested externally. Whilst there is no immediate load change, this is not detrimental. The polymers when leaving the bearing regain their original form and viscosity is regained. However, as bearing loading is increased, the polymers literally break up. The oil returns to its original, far lower, base viscosity and attendant strength. Not very useful in race conditions. The detergent and antiscuff additives used in these oils are of similar long chain make up and are similarly destroyed. For road car engines, where fuel and combustion by-products break down the mineral oil base very quickly, frequent oil changes replenish the additive package. This does not help the racing engine, that might destroy a viscosity modifier in minutes of high speed running.

An industry had grown up in the USA, where excesses of climate cause very fast oil degradation, based on oil additive packages. The major oil companies sell a high street product in bulk and cost of production is a very important factor. Oil additive companies offered high tech - and high price - lubricity agents, viscosity modifiers and detergent packages. Often known in the US as snake oils, some of these additives were not worth the value of the cardboard box in which they came. Others were genuine forerunners of the synthetic products in use today and became well respected. Names such as STP and Wynns are still, if not household names, recognised in most garages. Special competition oils to cope with these high revving engines using these types of additive were able to be produced. Nowadays we refer to such an oil as a semi-synthetic. High street oil companies, who were interested in connection with motor racing for its image, were happy to allow their own specialist competition departments or independent companies prepare these lubricants for them. The man in the street was quite happy to believe he was running the same oil in his motor as a Formula 1 car.

The next problem to rear its ugly head was that of oil aeration. Given enough oil in the system, big enough coolers and a nice big oil tank to let air bubbles separate from the oil, a mineral oil can cope with a lot, for a short time at least. Look at a Formula 1 car from 25 years ago and see the size of the oil pipes, oil coolers, pumps and filters. Where have they gone now? The main problem lies in the dry sump system of a race engine. To enable the crankshaft to be completely free from oil drag and to allow the engine to be mounted as low as possible, the engine oil is pumped from a shallow tray - instead of a deep sump, underneath the engine and sent to a remote tank. The feed side of the oil supply is then pumped from the tank rather than from the sump. In order to make sure the sump is always empty, the scavenge - sump emptying - pump has to be of much greater capacity than the feed pump. Air is thus sucked through this part of the system with the oil. Unfortunately, mineral oil will absorb air, sometimes as much as 25% in such conditions, which if left in the oil would present a bearing oil film full of holes like a Dutch cheese. A large oil tank with an air separator system is therefore essential. Similarly, a mineral oil when overheated breaks down to form tars and varnishes, therefore large oil pumps, large diameter oil pipes and hefty oil cooling radiators are a must, as is the maximum amount of oil possible on board. All this extra weight and aerodynamic drag was a complete anathema to racing car designers, but was it possible to get rid of it?

PAO based synthetics are less affected by fuel or by-products of fuel than oils with mineral bases, they give high film strength from low viscosity oils and have an inherent viscosity index which means far fewer viscosity modifiers are required. The PAO synthetic base also lasts far longer without breaking down. The perfect base oil? Maybe. Learn about other stronger synthetic base oils, how to get rid of bulky oil cooler systems from your Formula 1 car, and where Red Line® synthetic oils come into all of this, in the next exciting episode.