Amsoil SVG 75w90, 25K, 04 Chevy Tahoe

[TXHunter]

2nd rear diff UOA on the wife's new to us Tahoe. Oil was changed at time of sample. Blackstone comments at the bottom.

Make/Model: GM Differential
Vehicle: 2004 Chevrolet Tahoe

Code:


OIL Amsoil 75w90 Unknown

MILES IN USE 25,128 Unknown

MILES ON UNIT 148K 123K

SAMPLE TAKEN 3/18/13 5/3/11

MAKE UP OIL 0 0



ALUMINUM 3 4

CHROMIUM 1 2

IRON 255 672

COPPER 7 28

LEAD 0 1

TIN 0 0

MOLYBDENUM 0 3

NICKEL 4 11

MANGANESE 6 26

SILVER 0 0

TITANIUM 2 0

POTASSIUM 0 0

BORON 100 179

SILICON 162 13

SODIUM 6 34

CALCIUM 9 42

MAGNESIUM 3 3

PHOSPHORUS 913 1683

ZINC 21 68

BARIUM 0 1



SUS @ 210F 88.3 69.0

Visc @ 100C 17.57 12.70

Flashpoint 415 370

Fuel % 0.0 0.0

Antifreeze % 0.0 0.0

Water % 0.0 0.0

Insolubles % 0.5 0.2

TAN 1.8 NA


The new sample from your differential is looking better than the last one. Iron and copper made huge improvements and now compare favorably to universal averages. They show typical wear levels for a GM differential after about 32,400 miles on the oil. Silicon is kind of strange find. It can show abrasive dirt, but with wear this low we're betting it's an anti-foam additive used by Amsoil, or maybe a silicon sealer. No moisture was present and insolubles are okay at 0.5%. We have to do a TAN on diff fluid too and that read 1.8. Run the next oil 30-35K miles.

 

[dnewton3]

Everything looks to be settling down nicely.

You post so many different UOAs I cannot remember the history on each unit. Was the former UOA on factory fill or a long OCi? That would possibly explain the dramatic drop in Fe and Cu.

25k miles on Amsoil SVG is too short! Any dino would last way longer than that. SVG is one of the better gear oils out there; it can safely be extended much further.

 

[bama7x57]

I'd bet the first sample was FF.
I know for a fact my 01 Suburban is running the FF and it's highly probable my others are also.

 

[Rob_Roy]

Great report. Run the next fill for at least 50k.

 

[MolaKule]

Quote:
Silicon is kind of strange find. It can show abrasive dirt, but with wear this low we're betting it's an anti-foam additive used by Amsoil, or maybe a silicon sealer.


For sure, no one uses this amount of silicon as a defoamer, not even Redline.

Most likely RTV sealer or coating on gasket.

 

[TXHunter]

I'm not really sure if this was FF or not, we purchased the Tahoe used at 119K miles and none of the service records were provided. From the condition of the other components, I would not be surprised if this was FF.