![]() Let’s do a brief recap of what High Temperature High Shear HTHS is all about. In last month’s CAT magazine we took a look at HTHS viscosity. The oil manufacturers have included a set of HTHS viscosity rangesfor Low SAPS oils. Just reducing the amount of Phosphorous and Sulphur additives in Low SAPS oil is not the end of the story. ![]() (Alternative additives are used to ensure a balanced oil formulation that gives the same protection) In both instances ACEA set limits as to how much Phosphorous and Sulphur can be used. It’s when the oil thickens up and causes sludge) It too can block the DPF (Oil oxidation is bad news for any engine. The trouble is, that when it is burnt, it blocks the DPF - in addition the Phosphorous can poison the GPF (Gasoline Particulate Filter) in petrol engine cars. The Phosphorous is an anti-wear additive. ![]() Moving on to the Phosphorous and Sulphur: These are additives that are added to the oil. This is the residue that blocks the DPF when Phosphorous and Sulphur additives are burnt in the oil. The “SA” is Sulphated Ash, “P” is for Phosphorus and “S” is for Sulphur.Ī neat explanation is that certain additives are limited in Low SAPS oils – it is not an extra portion of additives. The important take is that the five Low SAPS oils all have specific specifications, they are just different – We will return to how different they are in a moment. It’s not a case of good, better and best as you go through the 1 to 5 categories. One question that is often asked is what is the difference between the five Low SAPS oils? We now have five Low SAPS car oils and two in commercial oils.ĪCEA - the European Automobile Manufacturers' Association gave the Low SAPS oils a specific specification starting with C - They follow a logical sequence of C1 C2 C3 C4 C5. In helpful oil industry fashion, one Low SAPS oil wasn’t enough. The oil manufacturers came to the rescue and developed a set of Low SAPS oils. Low SAPS oils suddenly became rather important because the DPFs were getting blocked by the oil that was available at the time. The higher HTHS should ensure greater oil film strength, independent of the additives which are meant to protect the engine when that film is insufficient.Let’s see if we can answer some of the common questions about Low SAPS oils and ease the brain strain and ambiguity!ĭiesel Particulate Filters, DPF, came on the scene in mid-2000 and more recently Gasoline Particulate Filters, GPF. Remember that film thickness is not the same thing as protection for a formulated oil - additives protect metal parts when the film is no longer thick enough to prevent asperity contact.Ģ) Correct, but I tend to think that or would be a better measure than However, the measure is typically taken at the higher temperature.ģ) A lower number and higher viscosity index will correlate with lower *pumping* losses, while higher-than-required HTHS will generate what is called "internal fluid friction" losses. When the film is too thin you tend to have higher friction because of metal-metal (actually AW film-AW film) contact. Any excessive film thickness "adds more protection", but also adds more fluid friction, generates more heat, etc. In this case an optimized number is preferable. HTHS correlates with film thickness under shear and hydrodynamic lubrication (e.g. Look at the J300 - the difference between a XW-20 and XW-30 in is 0.3cP, and you know there is a fuel economy difference there.
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