Amsoil 75w90, 30K, 04 Chevy Tahoe

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Oil was drained and replaced with another round of Amsoil SVG at time of sample. Nice to have a starting point since the first was the flush from the previous owner with unknown mileage/history.

Make/Model: GM Differential (Front)
Vehicle: 2004 Chevrolet Tahoe
Code:


OIL Amsoil 75w90 Unknown

MILES IN USE 29,386 Unknown

MILES ON UNIT 158K 123K

SAMPLE TAKEN 11/8/13 5/3/11

MAKE UP OIL 0 0



ALUMINUM 2 7

CHROMIUM 0 1

IRON 133 346

COPPER 5 8

LEAD 1 1

TIN 0 0

MOLYBDENUM 9 82

NICKEL 2 4

MANGANESE 2 5

SILVER 1 0

TITANIUM 0 1

POTASSIUM 1 0

BORON 95 89

SILICON 36 38

SODIUM 2 4

CALCIUM 12 80

MAGNESIUM 2 10

PHOSPHORUS 862 579

ZINC 41 90

BARIUM 0 1



SUS @ 210F 78.6 56.0

Visc @ 100C 15.16 9.07

Flashpoint 415 370

Water % 0.0 0.0

Insolubles % 0.2 0.3

TAN 1.7 NA


Oil Analysis Comments:
We're assuming this oil has been changed since the last sample, as wear metals and insolubles are reading a whole lot lower than last time. Nothing wrong with that. In fact, changing the oil has revealed excellent wear. This oil run is about as long as average, yet almost all wear metals are reading below average. We're not seeing any problems here. No moisture was found, and the viscosity was correct for a 75W/90 oil. The TAN was 1.7, showing little acidity in the oil. You could probably leave the next oil in 45,000 miles with no trouble. Check back then.
 
My (97) Tahoe was super low in the rear diff, had less than a quart in it when I bought it. Cleaned the magnet, added 8 oz MMO plus 2 qts of cheep gear oil from Autozone and drove it around for 1500 miles, mostly short trips. I did pull a trailer on a 200 mile trip without any issues.

The axle seals were wet and all the sludge buildup in the carrier had loosened up and was nearly gone thanks to the MMO. Replaced the outer seals and filled it up with FGR, I use that oil in all my vehicles as it is a very good gear oil from Amsoil... This is how I did my Differential flush.

If you do not know about FGR it's one of the first gear oils Amsoil made and its a premium GL5 75w90; unlike the marine GL4 or the 80w90 that is less expensive... Amsoil dealer since 1995
 
dhellman12 -

Excellent results! I'm presuming Blackstone did the analysis. TAN a bit puzzling, since two prior VOAs of SVG showed virgin TAN to be in the 2.5 range. I did see a VOA from Wearcheck for SVG that showed virgin TAN to be in the 1.5 range.
 
Thanks cool to see an analysis on Amsoil SVG 75W90.

I've been using it in my diffs for years, obviously no problems.

I have taken note when people who know a lot more about fluids than me have said that Amsoil gear oils are pretty good.
 
Dumping an unknown fluid certainly helps understand a starting point, and gets out any "unknown" fluid that may not have been appropriate; you rarely know for POs do or why, but at times they can be careless or downright abusive. Dumping fluids when the maintenance routine is in question is never a bad thing.

The second UOA was a bit short; again, trying to see the condition of the diff. But if 30k miles was a planned distance, and not on a whim, then I'd have used any decent GL-5 dino lube; that distance is not far enough to really task a good fluid.

I'd run the OCI out to 90-100k for this round. The diff was broken in long, long ago. There is nothing but normal numbers here. The SVG is a stellar product; one of Amsoil's best offerings. Take advantage of it! 45k miles as Blackstone suggests is a waste; double+ that. It's not like a front diff on a Tahoe is seeing any kind of severe use after all.
 
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