Weighted Average Piston Deposits

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With all the talk of piston deposits, formation, causes, and how to avoid them, thought it would be relevant to see how they're tested for. In order to evaluate piston deposits and oxidation thickening, the sequence IIIH is used.


Analysis includes visual inspection and:

  • Kv increase
  • Wear Metals
  • Total Base Number
  • Total Acid Number
  • Oxidation and Nitration.

For GF-6, and now GF-7, the WPD has to be at least 4.2. (higher the better). Unfortunately no change for GF-7.

GF-6 Motor Oils using Sustainable Base Oils


Here is an example from a white paper from Biosynthetic using estolides to help with deposit control. Not the only thing that can be used but this was an example of adding estolides to the formulation to help resist deposit formation.


1728396560190.webp

*Green line is where Amsoil scored back in 2014 on the IIIG double length test.

1728396341675.webp


1728396419792.webp




So if your engine develops deposits from neglected maintanence, or using subpar quality oil, use Valvoline R&P to clean up and then either stay with it or use a higher quality synthetic like the Mobil 1's, Amsoil's, HPL's etc....to keep pistons clean.
 
I know I'm Captain Obvious for some but remember this is what the pistons look like after a short while, and it gets cumulatively worse.

Notice how adding Grp II oil reduces the deposit formation, and that has nothing on the cleaning properties of POE. Note that Amsoil SS has an oxidation value of 48

(see here: https://bobistheoilguy.com/forums/threads/amsoil-ss-5w30.332031/ ) so it does contain esters, but not a huge amount. Molybdenum tends to increase deposits aswell, and Amsoil does have a bit higher than normal moly in it.

for comparison it would be good to add the valvoline piston pictures to the original post, they looked close to the Amsoil pics IIRC.
 
I know I'm Captain Obvious for some but remember this is what the pistons look like after a short while, and it gets cumulatively worse.

Notice how adding Grp II oil reduces the deposit formation, and that has nothing on the cleaning properties of POE. Note that Amsoil SS has an oxidation value of 48

(see here: https://bobistheoilguy.com/forums/threads/amsoil-ss-5w30.332031/ ) so it does contain esters, but not a huge amount. Molybdenum tends to increase deposits aswell, and Amsoil does have a bit higher than normal moly in it.

for comparison it would be good to add the valvoline piston pictures to the original post, they looked close to the Amsoil pics IIRC.
I always thought there was a equilibrium point for a properly operating engine. Basically that the accumulation doesn't just continue, but excess will flake/burn/remove in some way.
 
I always thought there was a equilibrium point for a properly operating engine. Basically that the accumulation doesn't just continue, but excess will flake/burn/remove in some way.
I don't think equilibrium is ever reached, eventually all engines end up with seized rings. If you use a clean oil that might be way past when the engine or vehicle is condemned for other reasons though, if not so clean that might be at 90k miles.....
 
I know I'm Captain Obvious for some but remember this is what the pistons look like after a short while, and it gets cumulatively worse.

Notice how adding Grp II oil reduces the deposit formation, and that has nothing on the cleaning properties of POE. Note that Amsoil SS has an oxidation value of 48

(see here: https://bobistheoilguy.com/forums/threads/amsoil-ss-5w30.332031/ ) so it does contain esters, but not a huge amount. Molybdenum tends to increase deposits aswell, and Amsoil does have a bit higher than normal moly in it.

for comparison it would be good to add the valvoline piston pictures to the original post, they looked close to the Amsoil pics IIRC.
Amsoil SS oxidation values for SS range from 48-62, consistently. You're right probably about 10% if I had to guess, maybe a tad more.

The Valvoline photos are nice. When you consider that prior to R&P, its been all about mitigating them over the life of the engine, it's truly an impressive/innovative product IMO.

Cleanup is important though, so the higher solvency based premium boutique oils are going to do a good job preventing deposits from forming.
 
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