MR VXS2
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An interesting read to say the least. I wonder which oils use what base group?
Have a read...
What about synthetic motor oils? Do they need Viscosity Additives?
Group IV (4) and Group V (5) base oil (synthetics) are chemically made from uniform molecules with no paraffin and generally don't need Viscosity Additives. However, in recent years Group III (3) based oils have been labeled "synthetic" through a legal loophole. These are petroleum based Group II (2) oils that have had the sulfur refined out making them more pure and longer lasting. Group III (3) "synthetic" motor oils must employ Viscosity Additives being petroleum based.
Group V (5) based synthetics are usually not compatible with petroleum or petroleum fuels and have poor seal swell. These are used for air compressors, hydraulics, etc. It's the Group IV (4) PAO based synthetics that make the best motor oils. They are compatible with petroleum based oils and fuels plus they have better seal swell than petroleum. Typically PAO based motor oils use no Viscosity Index additives yet pass the multi-grade viscosity requirements as a straight weight! This makes them ideal under a greater temperature range. One advantage of not having to employ Viscosity Improving additives is having a more pure undiluted lubricant that can be loaded with more longevity and performance additives to keep the oil cleaner longer with better mileage/horsepower.
How do I know what motor oil is a Group IV (4) based PAO synthetic motor oil?
As more and more large oil companies switched their "synthetic" motor oils to the less expensive/more profitable Group III (3) base stocks it has become much easier to identify which are PAO based true synthetic. Of the large oil companies, only Mobil 1 Extended Performance, as of this writing (12-16-2012), is still a PAO based true synthetic. The rest, including regular Mobil 1 and Castrol Edge have switched to the cheaper/more profitable Group III (3) petroleum based "synthetic" motor oil. AMSOIL Synthetic Motor Oils are PAO based true synthetic motor oils with the exception of the short oil drain OE and XL synthetic motor oils sold at some Auto Parts Stores and Quick Oil Change Centers. This leaves more than 20 PAO based true synthetic motor oils manufactured and marketed by AMSOIL with only a few Group III (3) based synthetic motor oils identified by the "OE" and "XL" product name.
So as you can see, the average performance of motor oils can be affected by how they change during their service life. Multi grade petroleum can lose viscosity and thin causing accelerated wear as the VI additives shear back. Straight weight petroleum (i.e. SAE 30, SAE 40) thicken a lot as they cool meaning longer time before lubricant reaches critical parts on cold starts, but have no VI additives so they resists thinning. However, they can degrade and thicken as heat and by products of combustion affect the unsaturated chemistry. Group III (3) synthetics resists this degradation much better, but being petroleum based employ some VI additives which is a negative and typically don't have as good performance in the volatility viscosity retention areas. Only the Group IV (4) PAO base synthetics have the saturated chemistry to resist degrading when exposed to the by products of combustion and heat, plus typically employ no VI additives making them very thermally stable for longer periods. For this reason the Group IV (4) synthetics maintain peak mileage and power throughout their service life
Have a read...
What about synthetic motor oils? Do they need Viscosity Additives?
Group IV (4) and Group V (5) base oil (synthetics) are chemically made from uniform molecules with no paraffin and generally don't need Viscosity Additives. However, in recent years Group III (3) based oils have been labeled "synthetic" through a legal loophole. These are petroleum based Group II (2) oils that have had the sulfur refined out making them more pure and longer lasting. Group III (3) "synthetic" motor oils must employ Viscosity Additives being petroleum based.
Group V (5) based synthetics are usually not compatible with petroleum or petroleum fuels and have poor seal swell. These are used for air compressors, hydraulics, etc. It's the Group IV (4) PAO based synthetics that make the best motor oils. They are compatible with petroleum based oils and fuels plus they have better seal swell than petroleum. Typically PAO based motor oils use no Viscosity Index additives yet pass the multi-grade viscosity requirements as a straight weight! This makes them ideal under a greater temperature range. One advantage of not having to employ Viscosity Improving additives is having a more pure undiluted lubricant that can be loaded with more longevity and performance additives to keep the oil cleaner longer with better mileage/horsepower.
How do I know what motor oil is a Group IV (4) based PAO synthetic motor oil?
As more and more large oil companies switched their "synthetic" motor oils to the less expensive/more profitable Group III (3) base stocks it has become much easier to identify which are PAO based true synthetic. Of the large oil companies, only Mobil 1 Extended Performance, as of this writing (12-16-2012), is still a PAO based true synthetic. The rest, including regular Mobil 1 and Castrol Edge have switched to the cheaper/more profitable Group III (3) petroleum based "synthetic" motor oil. AMSOIL Synthetic Motor Oils are PAO based true synthetic motor oils with the exception of the short oil drain OE and XL synthetic motor oils sold at some Auto Parts Stores and Quick Oil Change Centers. This leaves more than 20 PAO based true synthetic motor oils manufactured and marketed by AMSOIL with only a few Group III (3) based synthetic motor oils identified by the "OE" and "XL" product name.
So as you can see, the average performance of motor oils can be affected by how they change during their service life. Multi grade petroleum can lose viscosity and thin causing accelerated wear as the VI additives shear back. Straight weight petroleum (i.e. SAE 30, SAE 40) thicken a lot as they cool meaning longer time before lubricant reaches critical parts on cold starts, but have no VI additives so they resists thinning. However, they can degrade and thicken as heat and by products of combustion affect the unsaturated chemistry. Group III (3) synthetics resists this degradation much better, but being petroleum based employ some VI additives which is a negative and typically don't have as good performance in the volatility viscosity retention areas. Only the Group IV (4) PAO base synthetics have the saturated chemistry to resist degrading when exposed to the by products of combustion and heat, plus typically employ no VI additives making them very thermally stable for longer periods. For this reason the Group IV (4) synthetics maintain peak mileage and power throughout their service life
