GM Fluids VS. Amsoil
Thread Starter
Advanced
Joined: Jun 2025
Posts: 75
Likes: 31
From: Boston, MA
GM Fluids VS. Amsoil
In April or May I will be picking up my new, to me, 2017 GS M7 in NC and driving it 850+ miles home. The car has 17.5K miles on it and from what I gather, other than engine oil changes, all other fluids are original. I am speaking with a local performance shop about doing, the trans, differential and clutch fluids and they recommend Amsoil products. I would appreciate insights on this manufacturer vs using GM products.
Tech Contributor
Joined: Oct 1999
Posts: 41,037
Likes: 9,798
From: Charlotte, NC (formerly Endicott, NY)
If the car has had the oil changed and is at 17.5K miles, the only fluids needing change are the coolant and clutch fluid. The OM recommends changing the coolant every 5 years/150K miles and changing the clutch fluid every three years. If the coolant is the original coolant, it is long overdue for change (it should be coming up on its second change instead of its first change). The 5 year change interval works well and I have used it on all of my GM vehicles since I purchased my C5 in 1997. When changing the coolant, ensure you use the correct coolant mixture as the C7 uses a mixture of 40% DexCool/60% clear drinkable water. Purchasing a premix of 50/50 coolant will not work.
The transmission and differential fluids are not due for changing until the car hits 45K miles. I track my car and changed the transmission and diff fluids at much fewer miles, but the OM recommendation is fine for street-driven cars.
I used the GM fluids and they have worked well. I have never used AMSOIL fluids as I see no advantage. They might be better, but that doesn't mean they will actually lubricate the engine any better than the GM fluids will.
Bill
The transmission and differential fluids are not due for changing until the car hits 45K miles. I track my car and changed the transmission and diff fluids at much fewer miles, but the OM recommendation is fine for street-driven cars.
I used the GM fluids and they have worked well. I have never used AMSOIL fluids as I see no advantage. They might be better, but that doesn't mean they will actually lubricate the engine any better than the GM fluids will.
Bill
Drifting
Joined: Sep 2019
Posts: 1,908
Likes: 1,939
From: Colo Spgs, CO
You are wise to change those fluids and your car will be just fine with GM or Amsoil fluids. There are plenty of folks using both here in the forums.
Can't help but ask, if you trust the shop to work on your car, why not trust their fluid recommendations?
Can't help but ask, if you trust the shop to work on your car, why not trust their fluid recommendations?
Le Mans Master
Joined: Jun 2019
Posts: 5,430
Likes: 2,154
From: Loveland
When I purchased my 2014 I changed all of the fluids. There can be issues with a number of fluids not being correct, full, or done correctly. You never know what kind of monkey juice was put into your car. I would recommended the GM, ACDelco fluids. These aftermarket companies love to come up with there own version of correct fluids, even when they don't really meet OEM specs.
Thread Starter
Advanced
Joined: Jun 2025
Posts: 75
Likes: 31
From: Boston, MA
Reason I am asking is that I don't know the shop and only going by on-line recommendations and reviews. They are a chevy performance shop that really doesn't do routine maintenance but are willing under my circumstances.
Drifting
Joined: Oct 2005
Posts: 1,352
Likes: 715
From: Terrell North Carolina
As I have (2) C7's, one with 72K miles and (1) with 29K miles, I have always used the GM fluids with no issues. The clutch fluid will be DOT 4 fluid, and can be most any brand as it is a brake fluid. As other ops's have stated, the (2) main fluids Coolant & clutch need to be changed, but for my two cents worth, if I was making the drive you are planning, I would change all fluids, especially the M7 transmission, at it tends to be a bit nothy in the 1 to 2 shift & and fluid change has helped that issue some especially when the trans is cold.
Good luck & enjoy.
Good luck & enjoy.
Tech Contributor
Joined: Oct 1999
Posts: 41,037
Likes: 9,798
From: Charlotte, NC (formerly Endicott, NY)
Bill
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Race Director
Joined: Sep 2000
Posts: 11,139
Likes: 1,910
From: Missouri City, TX
In April or May I will be picking up my new, to me, 2017 GS M7 in NC and driving it 850+ miles home. The car has 17.5K miles on it and from what I gather, other than engine oil changes, all other fluids are original. I am speaking with a local performance shop about doing, the trans, differential and clutch fluids and they recommend Amsoil products. I would appreciate insights on this manufacturer vs using GM products.
Burning Brakes
Joined: Jun 2021
Posts: 801
Likes: 408
From: NC
Used Mobil1 0W-40 during the warranty period. Switched to Amsoil Signature 0W-40 and noticed engine was a tad quieter, but it comes out cleaner than the Mobil1 when I change it. I see many HP Corvette shops now use Amsoil such as Lingenfelter.
Racer
Joined: Mar 2013
Posts: 264
Likes: 338
From: NC
In April or May I will be picking up my new, to me, 2017 GS M7 in NC and driving it 850+ miles home. The car has 17.5K miles on it and from what I gather, other than engine oil changes, all other fluids are original. I am speaking with a local performance shop about doing, the trans, differential and clutch fluids and they recommend Amsoil products. I would appreciate insights on this manufacturer vs using GM products.
Melting Slicks
Joined: Nov 2007
Posts: 2,278
Likes: 550
From: Pittsburgh PA
St. Jude Donor '10-'11-'12-'13-'14
Instructor
Joined: Mar 2019
Posts: 168
Likes: 53
From: Mooresville, IN
FYI....
If you change your coolant and are mixing it yourself (not using premixed), make sure you use DISTILLED water !! Do NOT use tap water which contains minerals that may be deposited throughout your cooling system.
Also, you can't go wrong with Amsoil premium products.... I replaced the trans fluid on my Vette ('08 C6M) with Amsoil Signature series ATF and the trans shifts smoother.
If you change your coolant and are mixing it yourself (not using premixed), make sure you use DISTILLED water !! Do NOT use tap water which contains minerals that may be deposited throughout your cooling system.
Also, you can't go wrong with Amsoil premium products.... I replaced the trans fluid on my Vette ('08 C6M) with Amsoil Signature series ATF and the trans shifts smoother.
Race Director
Joined: Sep 2000
Posts: 11,139
Likes: 1,910
From: Missouri City, TX
Race Director
Joined: Sep 2000
Posts: 11,139
Likes: 1,910
From: Missouri City, TX
FYI....
If you change your coolant and are mixing it yourself (not using premixed), make sure you use DISTILLED water !! Do NOT use tap water which contains minerals that may be deposited throughout your cooling system.
Also, you can't go wrong with Amsoil premium products.... I replaced the trans fluid on my Vette ('08 C6M) with Amsoil Signature series ATF and the trans shifts smoother.
If you change your coolant and are mixing it yourself (not using premixed), make sure you use DISTILLED water !! Do NOT use tap water which contains minerals that may be deposited throughout your cooling system.
Also, you can't go wrong with Amsoil premium products.... I replaced the trans fluid on my Vette ('08 C6M) with Amsoil Signature series ATF and the trans shifts smoother.
Good point!! I use distilled water in my mix as my subdivision supply is well water with high mineral content.
Race Director
Joined: Sep 2000
Posts: 11,139
Likes: 1,910
From: Missouri City, TX
Another point for DIY’ers - Do not make the mistake in using an DEXRON 6 compliant ATF for a TREMEC M6 or M7 manual gear boxes!! It is too thin and was introduced as a more fuel efficient fluid for A4, A6 and A8 autos. The M6 and M7 manuals must use an ATF equivalent to the older (and now superseded) DEXRON 3 fluid. Examples of DEXRON 3 fluids are AMSOIL ATF, AMSOIL TorqueDrive, Redline D4, etc, all of which I have used in my Z vette M6 and M7 trannies.
Race Director
Joined: Apr 2014
Posts: 10,398
Likes: 1,700
From: North Texas
FYI....
If you change your coolant and are mixing it yourself (not using premixed), make sure you use DISTILLED water !! Do NOT use tap water which contains minerals that may be deposited throughout your cooling system.
Also, you can't go wrong with Amsoil premium products.... I replaced the trans fluid on my Vette ('08 C6M) with Amsoil Signature series ATF and the trans shifts smoother.
If you change your coolant and are mixing it yourself (not using premixed), make sure you use DISTILLED water !! Do NOT use tap water which contains minerals that may be deposited throughout your cooling system.
Also, you can't go wrong with Amsoil premium products.... I replaced the trans fluid on my Vette ('08 C6M) with Amsoil Signature series ATF and the trans shifts smoother.
I encourage you to look it up yourself.
Instructor
Joined: Sep 2016
Posts: 207
Likes: 34
Typically, DISTILLED water is NOT recommended for use in automotive cooling systems. Distilled water is "ionically hungry" and will strip electrons from the metals in your cooling system as it attempts to rebalance itself. Softened or filtered water is fine.
I encourage you to look it up yourself.
I encourage you to look it up yourself.
Le Mans Master
Joined: Jun 2019
Posts: 5,430
Likes: 2,154
From: Loveland
I also did not use distilled water, I used normal bottled drinking water.
I understand the confusion. Every place I look, it says to use distilled water.
But this is what the 2014 and 2019 C7 manual says:
From the manual>
"40/60 coolant/water mixture of clean, drinkable water and use only DEX-COOL® Coolant".
I think the reason is because the distilled water boils at a lower temperature.
The most difficult part of changing the fluid, is to get the correct 40/60 mixture.
I understand the confusion. Every place I look, it says to use distilled water.
But this is what the 2014 and 2019 C7 manual says:
From the manual>
"40/60 coolant/water mixture of clean, drinkable water and use only DEX-COOL® Coolant".
I think the reason is because the distilled water boils at a lower temperature.
The most difficult part of changing the fluid, is to get the correct 40/60 mixture.
Last edited by kodpkd; Jan 28, 2026 at 10:23 AM.