Are polymer based additives good or bad?

[Francis]

Hi all, a question for the smart ones.

Are polymer based additives good or bad?

I am trying to pick an oil, both are the same weight, both are the same rating, but one makes a point of saying the use a polymer based additives, the other claims using these involves a risk and there not good.

So not know that much about them or how they may be different, do you guy's know much about them?

Thanks!

 

[Francis]

Just incase your interested, this was the email that go me wondering all about this.

This from BP. "Corse plus contains a polymer based anti scuff additive that is extremely effective in preventing roller follower scoring as well as push rod gawling."

This from Valvoline. "Francis,
Additives including polymers can be a worry."

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[SteveS]

I remember BP Corse 50 (?) from years ago, maybe 12 or 15 years ago, and it was a spectacularly good racing engine oil. The heavy viscosity component was a high molecular polymer which was very effective.

I recall someone at BP New Zealand saying, and this may not be applicable everywhere, that for cost savings BP NZ had replaced the high viscosity polymer with a high viscosity mineral component, and Corse 50 became a mediocre lubricant.

Some polymers can give problems, viscosity index improvers (VIIs) are polymers, and some can contribute to sludging. However we can't make a mineral oil based multigrade without them.

Polyalphaolefins (PAO) are polymers, and they're the major synthetic basestock used in synthetic engine oils. Also you couldn't make a smoke-free two stroke motorcycle engine oil without poly-isobutene (PIB).

 

[MolaKule]

Many polymers are used to carry AW and EP additives, and certain polymers and esters can actually function as AW additives. Sometimes an ester and a polymer are used together or reacted together to attain a specific goal, such as AW or anti-scuffing/anti-galling.

I have no idea as to the context of Valvoline's ranting. They use VII polymers so this reply must be from someone in marketing, and not a chemist.

 

[Dr. T]

This is also a very good question. The standard reply would be "don't use an oil with a large vicosity spread because the VII's will shear and deposit in your engine causing sludge/varnish".

But, who says that they actually deposit? Why doesn't anything else in the oil deposit an cause varnish/sludge? Why wouldn't the VII's simply float around and eventually drain during the next OCI? In other words, why are they targeted as being the exclusive enemies of sludge?

 

[TallPaul]

I have heard that todays polymers are pretty robust and while a 10w30 and a straight 30 are both 30 weight oils and given the same viscosity at 100C, when things get too hot, the 10w30 will stay thicker than the straight 30 because of the polymers.