Red Line 75W110, 10.5k mi OCI, 150k mi, Cadillac CTS-V

[Emperors6]

Previous UOA is here. VOA is here. UOA history for this vehicle is available with this search: https://bobistheoilguy.com/forums/s...c[title_only]=1&c[users]=Emperors6&o=date&g=1. Notes from oil slip: "I stuck a "Digi-Sense Irreversible 6-Point Horizontal Temperature Label" on the rear differential and it indicated it reached 210F but not any hotter. So, the 75W110 was not necessary."

 

[Lubener]

From your recent report, I would be looking for a major malfunction within your differential instead of another UOA. Possibly a pinion bearing. Surprised you never mentioned any noises.

 

[Emperors6]

I put it in the same spot as when I used to track the car and I would get >300F on the sticker. I would check it after each track session, and when the sticker reached that temp the OEM diff warning light also came on to indicate the diff fluid went above 300F.

 

[JohnnyG]

The only time I saw a CTS-V in the dealers shop, it was in for a new rear diff. Keep up with the maintenance.

 

[Emperors6]

I have two gallons of Red Line 75W90 left. I will run short OCIs and change them with the engine oil and see how it does then, and then make a decision on what to do. Keep running short OCIs? Look for another gear oil to see if I can get better results? Not sure right now.

 

[Emperors6]

From your recent report, I would be looking for a major malfunction within your differential instead of another UOA. Possibly a pinion bearing. Surprised you never mentioned any noises.

I've never heard any noises from the backend of the car and it still handles pretty well. So, not exactly sure what the wear numbers mean. This diff has lasted 150k miles so far, if it has to be replaced soon, it's not that bad.

 

[MolaKule]

The general wear metal's trending is down, but the fact you track the car I don't see it going down any further.

Personally I prefer 75W110 as it is provides good all weather protection.

You may want to try Amsoil's SG in 75W110 and see if the trending changes.

 

[Emperors6]

Hmm, would you recommend even a 75W140 instead to help with the wear? Even HPL's? @High Performance Lubricants any suggestions?

 

[Emperors6]

I made a little chart of the Fe wear (vertical axis is logarithmic):

Based off of this table:

Oil	RL 75W110	RL 75W110	RL 75W90	RL 75W90	RL 75W90	RL 75W90	Fuchs 75W90	Fuchs 75W90	RL 75W90	RL Heavy	RL Heavy	RL 75W90	OEM
OCI Date	5/3/2023	10/15/2022	12/17/2021	3/16/2020	5/29/2019	12/7/2018	10/9/2018	11/24/2017	6/6/2017	11/7/2016	10/7/2016	7/22/2016	4/15/2016
OCI Length (km)	16970	20837	27222	12567	13338	3049	5714	24532	19241	4	12139	4803	21867
Al	0	1	1	1	1	0	1	2	3	1	1	1	1
Cr	2	4	2	1	1	1	1	0	1	2	3	3	6
Fe	527	545	485	121	127	82	242	94	163	224	306	381	812
Cu	31	23	21	21	8	19	15	21	1	1	2	2	0
Al/1k miles	0	0.1	0.1	0.1	0.1	0	0.3	0.1	0.2	400	0.1	0.3	0.1
Cr/1k miles	0.2	0.3	0.1	0.1	0.1	0.5	0.3	0	0.1	800	0.4	1	0.4
Cu/1k miles	2.9	1.8	1.2	2.7	1	10	4.2	1.4	0.1	400	0.3	0.7	0
Fe/1k miles	49.7	41.8	28.5	15.4	15.2	43	67.8	6.1	13.6	89600	40.3	126.9	59.4
Days since Start	2574	2374	2072	1431	1139	966	907	588	417	206	175	98	0

 

[wpod]

It the differential a clutch type posi? If so try more slip additive.

 

[Emperors6]

Red Line already comes with the slip additive already in there. How much more should I try?