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FAQs - Cars
Frequently Asked Questions about Redline Automotive Oils and Additives
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Q: What exactly is Synthetic Oil?
A: Synthetic oil has been defined by marketing men and more recently by the courts as any lubricant which doesn't have a naturally occurring mineral oil base-stock. Thus a higher sale price is realised for the oil even though the 'synthetic' base fluid may not be as good a lubricant as the mineral oil it replaces. Many of these 'synthetics' are produced by chemically treating oil shale and contaminated tars - otherwise waste products, and fall truly into the normal category of synthetic: being not quite as good as the original.
True synthetic lubricants were defined as those which do not rely on petro-chemicals to be produced. General characteristics are that far greater loads and temperatures can be withstood than the equivalent mineral or vegetable based lubricant. These lubricants have been developed specifically as lubricating oils for extreme conditions, for instance: turbine engines and extreme pressure gear trains.
The description 'synthetic oil' does not therefore necessarily indicate that it is better than a mineral equivalent.
Q: What is the difference between vegetable, mineral, semi-synthetic and synthetic oils.
A: Vegetable oils and animal fats have been used as lubricants since the first straight branch through the middle of a round stone became an axle. In areas where crude oil seeped to the surface ancient man made full use of it, for heating, lighting and lubrication. Very early on it was also discovered that mineral and vegetable oils don't mix!
Vegetable oils have very good scuff resistance. Mineral oils have very good film strength properties. In an ideal world, the two would be mixed together to produce a perfect match. Alas, this is not possible - a gummy mess occurs. Experiments have long been carried out to modify the chemistry of either type of lubricant to produce a viable mixture.
The most commonly occurring type of replacement lubricant, is the Poly-Alpha Olefin family. It has been argued, technically, that as these are derived from oil and coal waste, they should not be described as synthetic, however PAOs are recognised in marketing terms as synthetics as are the light oil factions from hydro-cracking heavy crude oil.
A family of chemicals known as di-esters, an off-shoot of the chemical industry, exhibit characteristics of vegetable oil and can be mixed with either type of oil. These were developed for early steam turbine use, where the high speed and high temperatures rendered mineral oils useless.
PE poly-ol esters are stronger and more temperature resistant relations to the di-esters, which can also mix with mineral or vegatable oil. These were developed for modern gas turbine use and have the highest strength and temperature resistant properties available.
High street synthetic oils are generally made up of a mixture of these three types of lubricant. With no guide to contents, it can be seen that lubricants labelled as 'synthetic' are therefore able to vary in quality quite considerably.
All Red Line Motor, Race and Gear oils use only poly-ol ester base-stocks.
The term 'semi-synthetic' is totally meaningless in a technical sense, but in real terms means more money can be charged for the product as the word 'synthetic' appears on the label.
Q) What do the numbers on the oil can actually mean?
A) In the 1930s 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
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Viscosity @ 100oC SAE Rating
cSt
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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
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Low temp rating Temp at which
oil is usable
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25w -5C
20w -10C
15w -15C
10w -20C
5w -25C
0w -30C 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.
Q) Should I use 'straight' oils rather than multi-grades?
A) In the 1960s multi-grade oils were 'invented'. (See answer to question above)
These were low viscosity oils which, with the addition of viscosity modifiers, became higher in viscosity as temperature increased than they otherwise would have been. A 'straight' oil of, say, 50wt would have a winter rating of perhaps 30w and so be unusable at 0oc and so have to be changed for a lighter oil for winter use. By treating a 20w30 weight 'straight' oil with viscosity modifiers it became a 20w50 and thus can be used down to minus 10oC. However the viscosity modifiers are not as strong as the base lubricant and more easily break down with high temperatures and heavy working and so for competition work it became the norm to use lubricants without viscosity modifiers. Modern synthetics such as Red Line® contain barely any viscosity modifiers as the nature of poly-ol esters allow them to be blended to suit the temperature range intended.
Q) How long should I leave between oil changes?
A) Generally we recommend twice the manufacturers recommended oil change interval. If you have an engine with a monitoring device, which suggests when an oil change is due, this may go up to three times the expected mileage. This is not only due to the exceptional detergent properties of Red Line® lubricants, but the poly-ol ester base-stocks do not break down with use or age as do those used by mineral or cheap synthetic based oils.
A useful guide to oil condition can be obtained from the dip stick - the colour of the oil is a good indicator of condition, the smell of the oil is a good guide to overheating and fuel dilution. Rubbing a drop of oil between your finger and thumb is a good test for oil lubricity, particularly if compared to new oil.
Q) What exactly is running-in?
A) Within a newly manufactured or rebuilt engine there are a number of sliding and rotating parts which, although machine finished to an acceptable standard, require actual operation before their full performance can be realised. The period of operation in which this takes place is called running in. The running in period allows the fit of components to be optimised by wear under light load conditions so that at full temperatures and loads further extreme wear or deformation of load bearing surfaces will not take place. Similarly, some parts expect the heat treatment and working of operation before they reach their designed finished condition.
Ball and roller bearings are finished to a very high standard as complete self contained units and require little operation to operate at their maximum performance. White metal bearings operating against freshly machined journals are very much dependant on the accuracy of machining and surface finish of the journal. In a mass produced engine the final fine surface finish of a bearing may well be offset by financial considerations and a short period of light load running will give a better finish. This is normally expected by the designer or engine builder.
The most significant part of the running in process is concerned with the piston rings and cylinder bores. Good compression retention is vital to efficiency and performance, for which the piston rings provide three major functions:
1) Provide a pressure seal to prevent blow-by of high temperature gases.
2) Form the main path for conduction of heat from the piston crown to the cylinder walls.
3) Control the flow of oil to the skirt and rings themselves in an adequate quantity while preventing an excessive amount reaching the combustion chamber with consequent waste and carbonisation.
Piston rings are now conventionally made of fine grained alloy cast iron, having excellent heat and wear resisting properties. The ring is formed with a gap in its circumference to allow for radial expansion both for thermal expansion and assembly on the piston but particularly to enable it to exercise flexible pressure on the cylinder walls.
A new ring which is initially circular, will not necessarily be so when slightly compressed or expanded in a new bore. The distribution of radial pressure around the bore is essential and the matching of the two is achieved during the running in period, thus final bore finish - however accurate cannot replace running in. The machining of the bore will not necessarily reflect the shape it will adopt after having passed through a number of heating cycles: uneven block shapes and eccentric loads from the block and cylinder head clamping can cause significant distortions.
In order to define how best to prepare a bore finish for initial running, we might examine what we are looking for in an ideal solution: the fuel air mix or the gases released on the burning of the fuel have a very low viscosity. These escaping gases are not particularly detrimental to the engine but do cause loss in pressure in the combustion chamber. To prevent this wasted gas force, we wish to create conditions down the side of the piston which induces large shear stresses on fluid which tries to escape - these shear stresses being sufficient so that fluid does not pass through, but will maintain a small gap between the bore wall and the piston ring. This will give a condition of maximum ring seal with minimum friction between
the piston and bore. A too highly polished bore surface - the phenomena of bore glazing for instance or a too highly finished bore on engine build, will provide the conditions in which the shear stresses are too low which causes loss in compression and power and burning of the crankcase lubricant, in a 4 stroke engine. Thus it can be seen that running in is a most critical part of engine preparation.
Q) How should I run my engine in ?
A) Although as we have seen, the processes we are trying to achieve are quite complicated, actually running in an engine is not difficult. In fact it is surprising that the process is so simple that it is ignored by so many..
Achieving the optimum surface of the bore before engine assembly is worth a whole book to itself, but we will assume a reasonable bore surface, either from re-boring and honing or just honing, both with new piston rings fitted, the following procedure should be followed. Run the engine for three or four sessions for 15 or 20 minute periods letting it cool after each period and gradually increasing the used rpm and load on the engine. A final session, finishing at full load and temperature conditions should have the engine ready for work!
On a dynamometer, crankcase pressure can be measured, representing the combustion gases passing the piston. This will be seen to drop during these running periods until a constant level is maintained. On road or track, similar measurement can be made by looking at the hydrocarbon (HC) output at the exhaust, but care should be taken to always measure at the same engine temperature and without adjusting the mixture! Again, a steady reading having been achieved, piston ring sealing is complete.
Modern lubricants have very efficient anti-wear packages as part of their make-up and can delay the very processes we are trying to carry out as quickly as possible during running in. In the worst case, the slipperiness and effectively of these oils can cause a too polished surface of the bore to be formed, thus preventing piston ring sealing at all. This is particularly prevalent in engines using cast iron rings in cast iron bores, such as the Honda Pro Kart engine. Indeed so effective are these oils that an engine which otherwise has rings which are perfectly bedded in can bore glaze and lose performance. Specialist oils are available to suit these engines, such as the 4 Stroke Kart Oil from Red Line. For initial running of all engines it is therefore useful to use an oil which is specifically blended for running in, or a cheap and nasty mineral oil, which is unlikely to have a very good anti-wear package. After running in, this oil should be replaced by a high quality fully synthetic oil as soon as possible!
It has been seen that correct piston ring sealing provides the perfect surface between bore and rings. Engine oil is not very slippery - there are no sliding components needing this in an engine, as there are for instance in a hypoid gear drive in a differential. There is no need for slipperiness additives therefore in an engine: they are only likely to cause bore glazing. Fairground salesmen have machines which show how their product can improve the slipperiness of oil. This could be done by the oil companies - there is no need!
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