Polymers and Synthetic Oil

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OK gang, since my oil knowledge is still somewhat limited even though I hang out here often, I thought I'd ask your clarification on this brief exchange I had on a Nissan newsgroup re: polymers and synthetics (quoted below). My question is still the same: if synthetics in fact do not use polymers to achieve wide viscosity ratings, then what do they use? And is it still as harmful as polymers so that you'd still prefer a narrower spread synthetic (say 10w-30) rather than a wider one (say 0w-30)? Thanks! [Cheers!]
quote:
>"BuddyWh" wrote in message >news:[email protected] >> The other great benefit of synthetic oil: dino oils use polymer >> viscosity index improvers to get wide viscosity (5w30) ratings. These >> polymer VI improvers break down leaving sludge, gum and varnish. >> Synthetics don't need these so they last much longer in service >> without gumming engines. To that, I replied: Why would synthetics not need polymers to achieve the viscosity spread? How do they accomplish it then? I thought both dino and synths use them. And to that he replied: Don't fully understand the chemistry, but here goes: Long chain polymer molecules added to oils are tightly coiled at lower temps and uncoil as it's temperature rises. This uncoiling thickens the oil as it heats and counteracts the base oil stock's thinning as it heats. That keeps it relatively thick at the higher temperature. It stands to reason that the wider the viscosity range of an oil, the greater the relative quantity of polymers added. Synthetic oil is much more stable so it simply doesn't thin as temperature rises so the addition of polymers is unecessary. Better synthetic oils don't have any added polymers at all.
 
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quote:
Originally posted by Jimbo: Polymer VI improvers are still needed to give synthetics a wide range like 0W-30 or 5W-40. These ratings are not available in "dino". Polymer technology has not stood still. The newer ones are supposedly more stable than even a few years ago. Maybe an Amsoil dealer tell us if any VI improver is in synthetic 10W-30, 15W-40 or 20W-50. I would think not. My understanding is that at least the old Mobil One (100% PAO) 10W-30 did not need any.
Also I don't believe the 10w30 Amsoil needs a VII. Can't say for the 15w40-20w50.
 
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Polymer VI improvers are still needed to give synthetics a wide range like 0W-30 or 5W-40. These ratings are not available in "dino". Polymer technology has not stood still. The newer ones are supposedly more stable than even a few years ago. Maybe an Amsoil dealer tell us if any VI improver is in synthetic 10W-30, 15W-40 or 20W-50. I would think not. My understanding is that at least the old Mobil One (100% PAO) 10W-30 did not need any.
 

MolaKule

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The full synthetic 10w30's and the 15W40's need little or no VII. It IS quite possible to formulate 0W30, 5W40, and 20W50 full synths with no VII. However, current economics dictate a little bit of VII.
 

MolaKule

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There are basically three kinds of VII's: !. PMA's or polymethylacrylates 2. Olefin Copolymers 3. Advanced styrene Copolymers; The last VII listed is used in Synthetic Fluids. [ March 14, 2003, 03:11 PM: Message edited by: MolaKule ]
 

MolaKule

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For ATF's and other hydraulic applications, another VII often used is Styrene Esters. Not only do they act as VII's, they also peform the role as Pour-Point Depresents (PPD).
 
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'Kule: "It IS quite possible to formulate 0W30, 5W40, and 20W50 full synths with no VII. However, current economics dictate a little bit of VII." Because the alternative would be higher concentrations of expensive esters? [Confused] --- Bror Jace
 

MolaKule

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"Because the alternative would be higher concentrations of expensive esters?" Correct. I don't think the truck and automotive market at this time could tolerate the cost.
 
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