Amsoil SVG 75w90, 45K, 04 Chevy Tahoe

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Will likely extend the next run to 55K based on Blackstone's recommendations. Overall looks like things are getting much better since we bought this one.

Make/Model: GM Differential
Vehicle: 2004 Chevrolet Tahoe

Code:


OIL SVG 75w90 SVG 75w90 SVG 75w90 Unknown

MILES IN USE 45,514 35,159 25,128 Unknown

MILES ON UNIT 229K 183K 148K 123K

SAMPLE TAKEN 10/29/17 4/16/15 3/18/13 5/3/11

MAKE UP OIL 0 0 0 0



ALUMINUM 1 2 3 4

CHROMIUM 0 1 1 2

IRON 102 264 255 672

COPPER 1 5 7 28

LEAD 0 0 0 1

TIN 0 0 0 0

MOLYBDENUM 0 1 0 3

NICKEL 2 4 4 11

MANGANESE 3 6 6 26

SILVER 0 0 0 0

TITANIUM 0 0 2 0

POTASSIUM 0 0 0 0

BORON 84 93 100 179

SILICON 81 145 162 13

SODIUM 4 5 6 34

CALCIUM 6 5 9 42

MAGNESIUM 0 2 3 3

PHOSPHORUS 745 884 913 1683

ZINC 5 13 21 68

BARIUM 0 0 0 1



SUS @ 210F 79.9 83.2 88.3 69.0

Visc @ 100C 15.50 16.31 17.57 12.70

Flashpoint 425 400 415 370

Water % 0.0 0.0 0.0 0.0

Insolubles % 0.2 0.2 0.5 0.2

TAN 2.6 1.4 1.8 NA


Blackstone comments:
This is the longest oil run across the page, so it's great to see iron so low. The other metals followed iron's example, so we don't see anything cautionary here. Silicon seems to be slowly washing out of the system. It's probably just additive or harmless sealer as opposed to abrasive dirt contamination. No moisture shows up and insolubles are very low. The viscosity is fine for 75W/90 and the TAN of 2.6 shows little acidity. Great report for your rear differential
 
It could have gone 2x the mileage with no issues. The majority of wear that occurs in an axle happens from 1-10K miles which is why the iron trends downward exponentially on a per mile basis despite the runs becoming longer and longer. I have seen this in every UOA posted UNLESS there was a problem with the axle.

You can see similar behavior in the UOAs of my 2010 FX4.
 
Quote:
The majority of wear that occurs in an axle happens from 1-10K miles which is why the iron trends downward exponentially on a per mile basis despite the runs becoming longer and longer. I have seen this in every UOA posted UNLESS there was a problem with the axle.


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The important thing is the ferrous metals are TRENDING downward.

In your environment I would use a 75W110 from Lubrication Engineers or Amsoil's SVT:

https://www.amsoil.com/lit/databulletins/g2043.pdf
 
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Where'd all that silicon come from? The SVG VOA shows 13ppm, and the original unknown fill didn't show much, so it looks like dirt got in at the first change. That could contribute to the high iron.
 
Originally Posted By: jaj
Where'd all that silicon come from? The SVG VOA shows 13ppm, and the original unknown fill didn't show much, so it looks like dirt got in at the first change. That could contribute to the high iron.
The higher silicon levels after the first OC could be from silicone gasket sealer. I tend to think with the first OC at 123K and a Fe reading of 672PPM that it may take a bit to wash out ( perhaps not 60K miles over two additional OC's though).
 
Based on the design of most rear axles (I presume that's what we're looking at here), we should agree than not all the lube comes out upon a drain cycle; a LOT is left in the tubes.
Therefore the very high Fe at the first UOA was probably the result of a very long OCI. Then the subsequent OCIs / UOAs are showing a downward trend due to much of the residual being drained out time after time.

I'd advocate for 75k miles at a min with the SVG; maybe longer.

At 229k miles, not sure how much life is left in the vehicle overall. Mechanically it may be OK? What about rust, etc? At what point do you start to pare down on the expenses? I'm not saying there's been a bad decision thus far, but more a question of where's the practical end of ownership versus the ROI on such expenses like Amsoil and UOAs???
 
This is really awesome sample set to look at, thanks for sharing you can see awesome trend. 600ppm iron and 23ppm copper to start and how sharply the copper dropped in next 20k miles and down from there. Another two or three 20-30k sets and iron and copper will be nice and low. Really impressed with this data set. Gives you general Idea of how long it takes to get diffs to really break in and everything to wash out. Well I shouldnt say break in but...Unserviced Diff going to nice clean one.
 
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