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#4550692 - 10/22/17 02:53 AM PPD and VII interactions in presence of biodiesel
Shannow Offline


Registered: 12/12/02
Posts: 39927
Loc: 'Stralia
biodiesel fuel dilution...

Evonik pesentation for STLE

Have posted before on the interaction between VII and PPDs, and some of the unhappy things that result.

This has some interesting charts, not just related to the topic of biodisel fuel dilution (some people in Oz have had sumps full of rubber from home brew biodiesel).

This chart is cool...a number of blends that contain different VIIs and DI packs (the couple of slides before this one list them and the oil properties.

An oil that's "in grade" with no PPDs, can end up out of grade with VII PPD interaction.



There's aged charts as well.

Have copped flack in the past for suggesting that cold temperature performance is the most likely to suffer with mixing fully finshed engine oils of different "design", but yet again, nasty things can happen iff the VIIs and PPDs do't play well.

That "yield stress" is part of the "W" requirements...it basically means that the oil is behaving as a semi solid "gel", that has to achieve the yield stress before (for example) falling into the void that's produced as the oil pump shifts the oil on a cold start. That's called "air binding" in the literature.

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#4550885 - 10/22/17 09:52 AM Re: PPD and VII interactions in presence of biodiesel [Re: Shannow]
CT8 Offline


Registered: 10/09/14
Posts: 11020
Loc: Idaho
There must be reasons why the oil change intervals are shortened when running biodiesel
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#4550898 - 10/22/17 10:01 AM Re: PPD and VII interactions in presence of biodiesel [Re: Shannow]
Cujet Offline


Registered: 02/15/03
Posts: 7164
Loc: Jupiter, Florida
We see the same thing here in the states. Those guys burning veggie based bio diesel often get polymerization of the oil. One guy documented his engine failure. It seems that long engine life requires good management and more than just a cursory understanding of what is actually happening.
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#4550983 - 10/22/17 11:55 AM Re: PPD and VII interactions in presence of biodiesel [Re: Shannow]
SonofJoe Offline


Registered: 07/23/16
Posts: 1052
Loc: Europe
I agree that the presentation is interesting but at the same time, you have to take it's overriding message with a huge pinch of salt.

Evonik are the biggest supplier of PMA PPDs for engine oils. To (ex) people like me, most PPDs are an easily manufactured commodity and you go for the one that does the necessary at the lowest cost. This is anathema to the folks at Evonik who have a vested interest in making the process of selecting PPDs as complicated as conceivably possible. I'm sure Evonik don't outright lie but they do tend to overemphasise VII/PPD incompatibility issues simply because they also supply PMA VIIs which provide both Viscosity Index improvement and MRV response (so no need to add a separate PPD). Whilst these sound great, the reality is that PMA-based VIIs are terribly inefficient and not a lot of folks use them.

It's well known in the industry that with high ethylene, crystalline OCP VIIs you need to take special care when selecting your PPD to avoid problems with MRV yield stress. Very waxy Group I base oils can also play havoc with PPD response but these days these are very rare beasts.

Finally, whilst this paper is all very technical interesting, it misses the essential point which is that the great bulk of PPDs that are put into engine oils are never ever called upon to actually DO anything! The engine oil market has moved to thinner and thinner engine oils, not only with lower KV100s but also with lower W-ratings. However the world hasn't gotten correspondingly colder! My own car specifies a 0W20. This oil contains a PPD but it would only ever be needed if the world entered another Ice Age!


Edited by SonofJoe (10/22/17 11:58 AM)

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#4554761 - 10/26/17 12:30 AM Re: PPD and VII interactions in presence of biodiesel [Re: Cujet]
Ducked Offline


Registered: 10/25/12
Posts: 4392
Loc: Taiwan
Originally Posted By: Cujet
We see the same thing here in the states. Those guys burning veggie based bio diesel often get polymerization of the oil. One guy documented his engine failure. It seems that long engine life requires good management and more than just a cursory understanding of what is actually happening.


Some people fail to distinguish between biodiesel and WVO, and "home brewed" biodiesel Shannow mentions above might be contaminated with unmodified waste oil which is a lot more unstable than biodiesel.

The presentation does seem to be talking about properly produced biodiesel though.

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#4564466 - 11/05/17 04:24 AM Re: PPD and VII interactions in presence of biodiesel [Re: Shannow]
Jetronic Offline


Registered: 02/27/09
Posts: 3653
Loc: down in the park
I'm more concerned that the used ppd in engine oils isn't effective on diesel or biodiesel, and as such fuel contamination which is seen as thinning engine oil, actually thickens it considerably below 30F... to the point that you ycant pump the oil if theres enough fuel present and the temperature ets low enough, regardless of using an appropriate W grade.
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