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post #22 of (permalink) Old 8th March 2007
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Part 1
Starting with a bit of a history lesson because it is needed to grasp the way oil is described and graded:
All engines require some form of lubrication, once it was by grease, then followed oil or grease that was manually pumped into the bearings as you went along, perhaps a couple of pumps on the old plunger every 1/2 miles or so until finally a mechanical oil pump was installed. This leap forward required a sump to keep the oil , pipe work to pick it up and pipe work to take it from the pump to the bearings. The manufacturer could get all his sums right but it relied on the oil to complete the equation; oil had to be graded so that its thickness could be specified. In simplistic terms early oil was graded by the time it took to flow a fixed amount through a hole of a given size. It was realised that temperature affected the oils ***8216;flowability***8217; (viscosity) so the measuring was carried out at 0degs and 100degs (not strictly true but you get the idea) So one oil of say 30 grade would flow at a certain rate when cold and at a certain , but much higher rate when hot . As manufacturers knew that a certain rate of flow was needed and that the grade of oil necessary to achieve this was different in winter to in summer you arrived at the situation when a car would require a different oil in the winter to the summer. In winter you might struggle to start the car as the oil of even a lighter grade was so thick when cold. Cars usually had a hand crank to turn them over as a final resort.
It was discovered that if you got a very light oil you could put in an additive called a viscosity improver (VI) which would stop the oil from thinning out so much as it got hot (most people think this is the other way around) This led to Multi grade oils that could even be left in all year around assuming that you didn't do much mileage as the oils could do with changing every 3,000 miles or so. This new multi grade oil required some rethinking in the way the oil was labelled as it certainly didn't fit in with the old classification system. This was done by giving the oil 2 numbers, the 1st followed by a 'w' which for ease should be considered to represent 'Winter' or the oils viscosity when cold (0 degs). The second number was the oils viscosity when hot (100 degs). This improvement in oil was limited by the fragility of the early VI's which would break down and leave you with the original thin oil incapable of maintaining its viscosity without the VI's when hot. The old ' oil like water' syndrome we all have seen. Over years these multi grade mineral oils improved tremendously, proper additive packages where introduced in an effort to counter rust, acids and the general by products of combustion, VI's became stronger but still the rule was that if the difference between the 1st number and 2nd was greater the strain on the VI' was more and the oil would be more likely to break down under strain, not so good. The performance of cars and their engines continued to improve, but the mineral based oils where reaching the limit of their development, Castor oils where used in high performance applications but still the lubrication was holding back engine development. High powered cars needed ever thicker oils to survive the strain of the pressure put upon them with regular changes to avoid the catastrophic effects oil degradation would have. It must be remembered here that Mineral oil is far from pure. In the oil will be components that even counteract the lubrication properties of the majority of the oil . A better way ahead was needed.
In 1972 Amsoil became the first synthetic motor oil in the world to meet American Petroleum Institute service requirements, But that as they say is another story.
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Last edited by amsoil; 8th March 2007 at 07:42 PM.
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