I know this is an old topic beaten to death...but it would be nice to get all the correct options in one place

What I am really looking for is, I recall from an old thread is that GM has a synthetic available...part number???? I assume it is a 5w30....seems it should also be available from Pennzoil

FWIW I have been running the Castrol for several years, very happy...but time to change

Thinking I want to go back to a 5w30.....perhaps a horsepower two less loss in the tranny..

Central Coaster....I think you have all the answers

I think GM still sells it... but Amsoil seems popular, too.

Was it Pennzoil or Kendall?

I dug this up one of my posts at CF. No p/n's and not sure if it's relabeled as anything else, but looks like you can at least get the alternatives at the dealer.

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Thin oil will definitely add hp. When my 4+3 was leaking gear oil, I'd know when to refill it because I'd start picking up ET (and noise) at the dragstrip I was at every other weekend. Unlike motor oil, the transmission is swimming in fluid.

If you aren't banned from the CF check here.

http://www.corvetteforum.com/forums/c ... -on-zf6-fluid-change.html

If you are let me know and I'll cut and paste the relevant stuff.

[quote]
CentralCoaster wrote:
GM Synchromesh Synthetic ($$, not sure if it's a direct replacement for the regular Synchromesh or not.)
quote]

The only GM synthetic I found is GM 12346190

http://paceperformance.com/index.asp? ... ion=VIEWPROD&ProdID=40902

Seems this is the same as Castrol SynTorq LT

This is not a synthetic synchromesh?????

http://www.stealth316.com/2-pennzoil-synchromesh.htm

Syn
General Motors (Part #12346190)

FM
General Motors (Part #12377916)

I use the Amsoil, works great.

Redline is another option.

I've seen nothing at all though to indicate Castrol's BMW engine oil was ever intended to be used in a transmission. There is no other application that uses it in a transmission.

The key to the TWS10-60 is the friction modifier for shearing forces.

It is designed for high RPM applications and turbo apps, such as the 911 Turbo.

IIRC all the trivia that comes together is sorta worked like this: BMW had a little problem with the I-6 in the previous M3 blowing up if revved at idle too much... the fix was to rebuild a few thousand motors and to add a rev limiter to limit unloaded revving.

I suspect that's when the 10-60 became the oil... there was an angle issue with the rod to crank that was causing the bearing failure. If I did some research I am sure I could find the real reasons... but a friction modified oil would make sense in this application.

I do not know if the oil was released to help fix the engine failures, but it wouldn't suprise me one bit!

I have been using the TWS for 100k miles and I don't know of any issues... it is sometimes hard to get into 1st... but that could be age and mileage (172k).

To test it, the next time I will try a different oil...

I've also been using the BMW oil for several years. It was convenient when both my street car and my track car used the same stuff...

I know that my situation is not necessarily relevant to those of you who daily drive your vettes; my car only sees occasional use, and that use is brutal and high revving. However, I've had no trouble at all and will continue to use the BMW oil in my trans.

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I am almost certain 12377916 is not for the ZF6...wrong specification numbers etc

GM #1052931 superceded #12346190 which is now obsolete

Seems Amsoil is the only synthetic oil that might be truly suitable for the ZF transmission...Royal Purple says thier motor oil is suitable but I honestly have my doubts..

BTW I stopped in a local Chevy dealer.....they don't stock either 1052931 or 12346190..plus they don't have a clue!!

On another subject.... Wonder why GM is in trouble....they had one tube of normal chasis grease available for $16.95 a tube!!!!!! I had $115 to spend based on a class action lawsuit against this dealership so no discounts were available and the $115 went real fast....

My first oil change was the oil from the BMW dealership. The trans was a little quieter but always had a intermitten shifting catch into 3rd. Next oil change I switched to the AmsOil Synchromesh and it was like "a rebuild in a bottle"! Much smoother shifting in all gears. It has some additive that is specially for brass synchros like the ZF6 has, and it apparently cleaned up mine to where it works like new again. I'm sold on the AmsOil.

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What specs should it have?

Did you compare with specs from the original fluid that has long been discontinued and superceded?

It would be interesting to compare with the BMW oil. It would look nothing alike and might get the attention of a few of these people that take internet stories as gospel.

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What internet story? The one that says the BMW oil is recommended fill for the ZF6?

That's one.

The only thing I've ever come across is an email from a ZF North America sales rep saying the TWS was recommended.

ZF meanwhile, has a long list of approved lubes for all their applications, and there are a bunch listed for the ZF S6-40, some look pretty bizarre. But the BMW oil is not on that list.

I guess I wasn't aware that was considered a "story". I emailed ZF a few years ago and was told that the GM fluid, BMW/Castol TWS 10w60 and a select list of ATF were all acceptable for the S6-40.

Do you have the email btw? I'm sort of curious if the person answering it actually knows the answer or if they just like having an answer.

It's hard to ask them that without sounding insulting. But seriously, how does this guy have the answer when ZF doesn't even publish it? Well, it is on their website, but they have 3 different answers to the same question.

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Unfortunately, I don't have the email anymore - that was about 6 years ago. I do remember that the guy's name was Martin Vogel (I can't remember what I had for lunch but I can remember that?). I may still have the list he sent - it was in a Word doc that I think I printed out and stuffed in the car file.

EDIT:
My last 2 changes have been with the BMW stuff and I have been pleased with the results but I'm probably going to try the Amsoil MTF next time (15k miles or so). No particular reason. Altho, CC's suggestion in that Cf thread of Canola and Mayo might be worth a shot.

I guess basically, the Castrol recommendation doesn't make sense to me given all I've read on the topic, and I've seen enough questionable experiences, including my own, and the analysis by Bill Bordreau to look elsewhere. I don't have any data comparing the various offerings though, so all I can really say is:

1. There is no consensus that Castrol is the correct fluid to use.

2. Do your own research, because neither Bill B., or Martin Vogel, or GM, or anyone else with a recommendation, is going to give you a free transmission if yours fails.

This is from Bill's website:

(Q.) I just bought, at the local BMW dealership, 3 liters of the Castrol TWS 10W60 oil. I was surprised to see that it is motor oil. Not being a lubrication engineer myself, who did the investigation and determination that this product is compatible with and good for our ZF transmissions? Jim – Grand Sport Registry

(A.) Jim, the C4 Corvette ZF S6-40 6-speed transmission uses engine oil for lubrication. I was told by Jeff Henning, Warranty Administrator of ZF Industries North America, that Engineering of ZF Industries in Germany determined that the BMW imported Castrol (RS superseded by TWS) 10W-60 oil was the recommended alternative to the (GM P/N 1052931) factory-fill oil for use in the ZF S6-40 transmission. In effort to verify ZF Industries alternative lubricant recommendation, we ran our own test series on the BMW imported Castrol TWS 10W-60 oil. Independent testing of the transmission oil samples was sub-contracted out to CTC Analytical Services. The test series went as follows:
<1> Spectrographic analysis indicated that it is has full synthetic composition.
<2> After 2 hours of operation, approximately 100 miles, oil sample analysis tests indicated that the viscosity rating was reduced from 60 down to a 43 level. No need to worry, this is a normal occurrence for this heavier type of oil. I attribute this to microscopic-level lubricant-strand trimming through operational loading where all of the oil contents has been passed through gear pressure-loading regions at least a few times.
<3> At 200 miles, the viscosity level stabilized at a 42 level viscosity since the 100 mile oil analysis test results.
<4> At 5000 miles, the oil analysis test results indicated a 40 level viscosity.
The test-transmission was completely disassembled and checked for wear. There were no signs of carbon film like experienced with the factory-fill oil. The phosphor-bronze lined synchronizers had no glazing and experienced an average mass loss of approximately 4% based on reserve-wear-range mass equivalency between 0.062"(new) and 0.048"(spent)
gap wear/mass measurements.
<5> At 10,000 miles, the oil analysis test results indicated a 39 level viscosity.
<6> At 12,500 miles, the oil analysis test results indicated a 37 level viscosity.
<7> At 15,000 miles, the oil analysis test results indicated a 34 level viscosity.
The test-transmission was again completely disassembled and checked for wear. There were no signs of carbon film like experienced with the factory-fill 30 oil. The phosphor-bronze lined synchronizers had no glazing and experienced an average mass loss of approximately 17% based on reserve-wear-range mass equivalency between 0.062"(new) and 0.048"(spent) gap wear/mass measurements.
<8> At 15,000 miles the oil had enough phosphor-bronze particles suspended
in it that deposits began building up inside of the synchronizer sliding
sleeves from the normal centrifuge-like rotational occurrence.
In Conclusion, until someone invents a copper magnet, we recommend that the ZF S6-40 6-speed transmission oil be changed at 10,000 - 12,000 mile intervals so as to minimize the amount of deposits of the suspended spent synchronizer material from collecting in critical component contact surface areas.

Is that the study you are talking about?

I disagree. He merely tested what Jeff Henning told him to use, and apparently doesn't have any better ideas.


He did not perform this test on any other fluids for comparison.

The Castrol's viscosity broke down quickly.

The synchros were 17% gone at 15,000 miles and the fluid was a bronze milkshake.

The factory fill produced a carbon film, ok so?

I think some people forget that Bill Bordreau is a transmission rebuilder, not a lubrication engineer.

I would be very interested in the same study done with other fluids as well. Anyone wanna sponsor that?

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I agree.
Just changed my GM bought fluid with 20K on it(I should add it looked in a sorry state, there was a visable copper sheen to it and it was quite dark, which surprised me but it shifted fine) to Amsoil MTF and it shifts just fine both cold(by my standards)normal and high RPM; if there is any change it is less notchy between 2nd and 3rd.