This was the first run on Amsoil ATF after switching from the GM Auto-Trak II fluid. I'm not sure how to explain the really high insolubles or copper? Fluid was replaced with another fill of Amsoil ATF at the time of this sample.

Make/Model: GM Transfer Case (Rebuilt)
Vehicle: 2004 Chevy Tahoe

Code:
OIL		Ams ATF	GM AT II	GM AT II
MILES IN USE	30,376	30,020		30,503
MILES ON UNIT	90,899	60,523		30,503
SAMPLE TAKEN	1/26/18	3/29/16		8/3/14
MAKE UP OIL	0	0		0

ALUMINUM	8	8		10	
CHROMIUM	0	0		0	
IRON		81	164		236	
COPPER		46	23		24	
LEAD		5	4		8	
TIN		0	0		2	
MOLYBDENUM	0	0		1	
NICKEL		3	3		3	
MANGANESE	60	17		16
SILVER		0	0		1	
TITANIUM	1	1		1	
POTASSIUM	0	2		0	
BORON		265	60		28	
SILICON		23	40		135	
SODIUM		36	62		68	
CALCIUM		227	55		38	
MAGNESIUM	90	56		51	
PHOSPHORUS	602	249		155	
ZINC		123	148		212	
BARIUM		0	1		3	

SUS @ 210	49.1	56.0		47.2	
cSt @ 100	7.00	9.07		6.41	
FLASHPOINT	425	435		425	
WATER %		0.0	0.0		0.0	
INSOLUBLES %	0.9	0.1		0.1	
TAN					0.9


Blackstone Comments:
This oil was in use about the same interval as the last and iron improved a lot. Aluminum and lead stayed steady, and copper doubled. Copper shows some extra brass/bronze wear, but with other metals in good shape, we aren't sure copper shows trouble. It's something to watch, but if the transfer case functions proprerly, let's just see how copper trends. Insolubles were quite high this time. 0.9% is a lot of solids so this was a good time to change this oil. Maybe those solids are related to the brass/bronze wear. Try ~30K miles again next time.


05 Kawasaki BF750 - 265hrs
12 Jeep 3.8L - Toyota 5w30 63K
04 DMax 6.6L - Amsoil AME 15w40 226K
04 Tahoe 5.3L - Amsoil ASL 5w30 238K
00 WS6 5.7L - Amsoil ASL 5w30 254K