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CT5-V 6 speed and rear diff. fluid recommendations brand etc.

CT5-V Model

BigBrett

Active Member
Joined
Jul 29, 2025
Messages
32
Location
Myrtle Beach
V-Series Cadillac(s)?
2025 CTS5V 6 speed
Hey all I have a 2024 CTS5V BW with 6 speed manuals, I have seen comments where guys are swapping out the OE fluids in trans and rear. what brand seems to be the go too, I have been a loyal amsoil guy in my other stuff, but curios what you all are using, I need it to keep warranty in speck as well, thanks
 
what's wrong with the OE fluid for the rear diff. There is a clutch pack and I would be concerned about blowing up my warranty with aftermarket. For the tranny HP-MFT works.
 
Nothing if that seems to be what everybody is doing I am ok with it.
I read guys using royal purple in trans saying it shifts better etc. just trying to see what others do.
I was going to have dealer do oil change and see about the others.
 
I've been/was an Amsoil user probably since before you were born, seriously. (I can say that since I'm old now, eghads) I mean I had a toilet paper filter on the firewall (in the 70's) fitted with the factory filter relocation adapter. Good times! I had Amsoil in everything! front to back but haven't bought it now for decades. I swore by the stuff but lost interest. Until now.

I could very well switch from Mobil 1 after another fluid flush, if it makes sense. The rear diff is gonna get Delco because I already bought the jugs but if I track the car it will need another flush after. hmmm. worth it?
 
I've been/was an Amsoil user probably since before you were born, seriously. (I can say that since I'm old now, eghads) I mean I had a toilet paper filter on the firewall (in the 70's) fitted with the factory filter relocation adapter. Good times! I had Amsoil in everything! front to back but haven't bought it now for decades. I swore by the stuff but lost interest. Until now.

I could very well switch from Mobil 1 after another fluid flush, if it makes sense. The rear diff is gonna get Delco because I already bought the jugs but if I track the car it will need another flush after. hmmm. worth it?
Yeah, i was going to use GM in rear, as that seems to be the best bet, with warranty, the guys i have seen do the 6 speed like royal purple or others? i guess the OEM stuff is OK. just seeing what everyone was using or had tried and results
 
I've been/was an Amsoil user probably since before you were born, seriously. (I can say that since I'm old now, eghads) I mean I had a toilet paper filter on the firewall (in the 70's) fitted with the factory filter relocation adapter. Good times! I had Amsoil in everything! front to back but haven't bought it now for decades. I swore by the stuff but lost interest. Until now.

I could very well switch from Mobil 1 after another fluid flush, if it makes sense. The rear diff is gonna get Delco because I already bought the jugs but if I track the car it will need another flush after. hmmm. worth it?
I also checked the Amsoil is not Dexo R certified. so, i won't go there, Mobil 1 is the only GM certified oil that I found on different websites?
 
I also checked the Amsoil is not Dexo R certified. so, i won't go there, Mobil 1 is the only GM certified oil that I found on different websites?
hmm, glad you mentoned it - I though I bought R but did't, just plain old Supercar 0W-40 dexos case code 126870. I can't believe the missing R got past me, I meant to get the R. Actually, the dealer did say it was the same. It was mentioned here before the difference, if any. I'm def using the Declo filter PF64 but man are they teeny-tiny.

14qts from Rock Auto and 12qts from Cherolet dealer in person, same Mobil 1 stuff from each. Probably the old stuff /not worried but I'll keep an eye out. Walmart had the non-R was well.
 
Yeah, i was going to use GM in rear, as that seems to be the best bet, with warranty, the guys i have seen do the 6 speed like royal purple or others? i guess the OEM stuff is OK. just seeing what everyone was using or had tried and results
I really want to put some slick stuff in the TR-6060. Mine is nowhere close to broken in but the shift linkage feels cranky - it's stiff and not that great at the monent. I don't like the "gate"of it right off the bat either- its off to me or my memory. I'll get used to it but if there's one place I'd put boutique lube it's the TR-6060 somehere, inside or linkage. Oh well, it'll probably grow on me once I learn how to drive the thing.
 
OP, don't over think it. the AC Delco OEM gear oil is very good. From my experience with two Camaro ZL1 6 Spd Tremec manuals, there's no advantage to going with a 3rd party gear oil.
 

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