JCtx

The purpose of this thread is to know which fluids are fully synthetic, and which ones work better than stock in owner's opinions, so please don't post Amsoil tests or crap like that .

Let's start with GM. DIFFERENTIAL first. Just bought 3 bottles of ACDelco Dexron LS 75/90, which is the recommended fluid. Reason I bought it is because I haven't had any binding issues with my differential. But most important of all, several people reported it was FULLY SYNTHETIC. Well, the bottles only say 'ACDelco Dexron LS Gear Oil 75W/90'. No word at all of being synthetic. Seems very weird to me a manufacturer (they always exaggerate everything) wouldn't put fully synthetic (or even synthetic blend) if it actually is. Does anybody have an MSDS on this? I'll obviously use them this time around. But if it's not fully synthetic, next time would use Mobil1 or RP MaxGear 75W/90 gear oil.

TRANSMISSION. What exactly does GM use for our TR6060 trannies? Is it a motor-oil based fluid, or ATF based one? And again, is it dino, a blend, or fully synthetic? On this, I read it's dino, so plan to change it. I used Redline MTL on a T56, which is basically the same thing as ours, and it broke down quickly, so don't plan to ever use that again. Having said that, if our fluid is ATF based, the correct Redline fluid would be the D4 ATF, no? The ones I'm debating about are RP Synchromax (supposedly ATF based) and Mobil1 silver bottle (Dexron III, and also ATF).

My main question on the tranny fluid is if it uses 'ATF-based' fluid, like it seems to be the case, can we just put straight ATF, since Redline D4 ATF and Mobil1 is exactly what they are??? RP Synchromax could be straight ATF or ATF-based manual transmission fluid; don't know for sure. But shouldn't we use the latter due to synchros possibly requiring different friction than torque converters to shift smoother? I definitely want to change the tranny fluid brand, not only because OEM doesn't appear to be synthetic, but because tranny is very notchy with OEM fluid... and it has always been.

Finally, I'll change engine/tranny/diff fluids at the 3K mile mark (currently 800). And every 2 years thereafter, which equates to about 10K miles (max) in my case. So I don't need the absolute longest lasting fluids out there, but what WORKS BEST on our cars . That's why I don't want to waste time debating tests, since any synthetic fluid would give me the protection my car needs. Heck, any dino oil probably would too, but synthetic provides better cold/start-up protection, so that's what I'll use . Let the debate begin .

gsflyer2011

Way to go JC!

I guess you meant Royal Purple Synchromax in your second paragraph?. My query is the same as far as the OEM differential fluid,the Amsoil white paper compares bunch of differential fluids including the so called GM Synthetic 75/90, I was unable to find a reference to that product in any GM parts unless they are talking about the GM dexron LS gear oil recommended for our differentials.

JCtx

Indeed. Brain fart corrected . Thanks for pointing that out.

I remember seeing a silver bottle of GM synthetic 75/90 fluid at one time. What I got this time is a black bottle of 'AC Delco', and no mention of being synthetic at all. And at $17 a bottle (plus shipping), I feel like I might have been ripped off man . Hope we get some answers later on.

Streetk14

JC, the dexron LS is definitely synthetic, and comes with a special friction modifier blend for these diffs. I just changed out the original fluid in the low-mileage Z06 diff I swapped in. As you probably know, I have a big drum of the Castrol XJ 75w90 synthetic at my disposal, but I went with the Dexron LS that I had to pay for.

For trans oil, I'm actually running pennzoil synchromesh. It's a semi-synthetic, but ammsoil makes a full synthetic version. Synchromesh is the only fluid recommended by Rockland Standard gear (rsgear.com), which is who built my new Tr6060. They are Tremec's top recommended custom builder, for what it's worth.

JCtx

Hey man, thanks for dropping by . Great to hear the Dexron LS is synthetic; will stick with it then. I also had some SAF XO 75W/90 left, but am using it on my BMW K1300S.
As far as the tranny, do you know if GM specs ATF-based fluid, or is it straight ATF, the same stuff that goes in automatics? Curious about that, as well as what the Pennzoil Synchromesh is. Your tranny was modified, so it might not be comparable, but just for the sake of argument, did you feel any difference from stock, especially on cold notchiness, and the 1-2 shift, and downloading into 2nd? Thanks again. Have a great weekend everybody.

HOXXOH

It sure makes one wonder why someone takes a brand new car and wants to change all the fluids immediately. There's a maintenance schedule in the owner's manual that indicates the recommended intervals. Doing them sooner without an overwhelming reason will not make your car perform better or last longer.

Your profile only shows appearance mods and you state that you only plan to drive about 5K miles annually. Most people that fit your profile never drive their cars anywhere near hard. So the chances of even needing an oil change in the first 10K miles is only because of the recommendation that it's done a minimum of once annually.

The factory carefully selected lubricants that were compatible with the tolerances and materials of the components they built. Or conversely, engineered to match available lubricants. To arbitrarily change fluid because it doesn't say synthetic on the bottle can get you into as many problems as you think it resolves.

You asked what fluids are better than stock. For the way you plan to drive the car, the answer is none.

However, it's still your car and your money, so you can do what you want.

C66 Racing

If you really want to see how your fluid is performing, have it tested. Here is an example of how well the stock GM fluid did in the diff of my 06 CTS-V (now sold).
CTS-V Factory Fill Diff Fluid Used Fluid Analysis

FYI, GM uses part 88861800 in the manual trannies and it is not synthetic. The spec for the tranny from GM has varied over the years. It used to be Dex III, which is a superseded spec. Dex III was both a GM brand name and a fluid spec. Both no longer exists though many companies still make fluids to the superseded Dex III spec. GM replaced the spec and the brand name with 88861800 after they came out with Dexron VI. Note that Dexron VI is also an ATF and they are not the same. GM originally said the Dexron VI would be backwards compatible in all applications including manual transmissions and they discontinued Dexron III when they came out with Dexron VI, which has a viscosity much lower than Dexron III. They quickly backed off of their position, issued several TSBs saying not to use Dexron VI in manual transmissions, then re-released Dexron III with a new part: 88861800. The caution is that ATF doesn't mean much. There are many low viscosity ATFs on the market today, and these are not what you want to use in your manual. You want to use an ATF that is designed for Dexron III. I use the AMSOIL Torque-Drive Synthetic Transmission Fluid (Product Code ATD1G) at the track and have been for many years without any transmission failures. Red Line D4 ATF is another example. But be wary of ATFs labeled for Dexron VI applications - these will be the low viscosity fluids that I would not use in your manual.

Note that you use the term ATF and MTF based as if that changes the basestock, which it does not. The basestock can be one of the below, or a blend:
Group I base oils are the least refined of all of the groups. They are usually a mix of different hydrocarbon chains with little or no uniformity. While some automotive oils use these stocks, they are generally used in less demanding applications.

Group II base oils are common in mineral based motor oils. They have fair to good performance in the areas of volatility, oxidation stability, wear prevention and flash/fire points. They have only fair performance in areas such as pour point and cold crank viscosity. Group II base stocks are what the majority of mineral oil fluids are made from.

Group III base oils are subjected to the highest level of refining of all the mineral oil stocks. Although not chemically engineered, they offer improved performance in a wide range of areas as well as good molecular uniformity and stability. By definition they are considered a synthesized material and can be used in the production of synthetic and semi-synthetic lubricants. Group III is used in the vast majority of full synthetics or synthetic blends. They are superior to group I and II oils but still have limitations. Some formulations are designed for extended oil changes. Almost all off the shelf synthetics today are Group III.

Group IV are polyalphaolefins (PAO) which are a chemically engineered synthesized basestocks. PAOs offer excellent stability, molecular uniformity and performance over a wide range of lubricating properties. PAO is a much more expensive basestock than the highly refined petroleum oil basestock of Group III.

Group V base oils are also chemically engineered stocks that do not fall into any of the categories previously mentioned. Typical examples of group V stocks are Esters, polyglycols and silicone. Red Line uses an ester basestock.

The API does not define any of the above as either synthetic or not synthetic. Advertising rulings in the U.S. allow Group III, IV and V to be labeled synthetic. In Europe, only Group IV and V can be labeled synthetic.

Most tranny fluids are Group II. Synthetic fluids can be Group III, IV or V. Most are Group III. AMSOIL's are predominantly Group IV and Red Line uses Group V.

Note that one of the key differences between ATF specifications and MTF specifications is the viscosity. GM specified a Dexron III ATF spec in the T56. The Red Line D4 ATF as an example Dex III ATF has a viscosity of 7.5 cSt at 212F. The Red Line MTL has a viscosity of 10.5 cSt at 212F. The Red Line D4 ATF is the proper fluid for the T56. FYI, the Dexron VI fluids have a viscosity down around 6 cSt at 212F.

JCtx

Thanks a lot for that explanation .

On the differential, you linked a 2007 case, and I believe the Dexron LS fluid came out after that, no? Plus the CTS-V is a totally different car than an LS3 Vette (way more TQ, HP, and weight), even if they share the same differential. At any rate, that's why I always change fluids early in all my new cars, to remove all the break-in metal shavings from the fluid. This is especially critical if there's not a magnetic drain plug present, which I believe is the case for our differential. You have all that metal in your fluid grinding the gears to an early grave. That could explain the higher wear compared to 'universal' averages. Or the differential could be too weak to handle the torque and HP on such a heavy car. Or both. Thanks again for your thorough post .

HOXXOH

Thanks for the laugh. Since you plan to drive only 5K miles a year, and not agressively either, the chances of the differential reaching a grave are less than you finding that final resting place. GM determined the failure rate on the factory fill is so low that they don't even have a recommended change interval.

Streetk14

Maybe so, but I'd still do my own "run-in" service on the trans and diff for the small cost. GM might not specify such things, but all BMW M cars get the powertrain fluids (engine, manual trans & diff) changed at 1200 miles -- and they (BMWNA) pay for it. Keep in mind these cars also come filled with synthetic, lifetime-fill fluids. If there was no benefit to component life, I doubt they'd invest what they do in it.

GM also doesn't recommend ever changing your brake fluid, even though it's hydroscopic. Most high performance manufacturers recommend changing it every 2 years or so. GM doesn't recommend it, but I still do it.

Streetk14

GM recommends an AFT-based fluid. I changed the original fluid in my trans before I broke the main shaft, and used the original GM "manual transmission and transfer case" fluid. It's a non-synthetic ATF type of fluid. That's really all I know.

As for my trans being modified, it is, but probably isn't much different than yours. It uses all factory Tremec parts, as far as I know. The synchros have been updated to the improved 2011+ parts, but with carbon blocker rings on 1-4 gears (factory is only 1-2). The synchromesh is recommended because it really helps with shift quality and the grinding issues a lot of these TR6060s have.

I was amazed at how good my trans shifted on the first drive, but I was used to the loaner '06 Z06 T56 I'd been running in the car for the 6 months. Not sure how much of that is the fluid and how much is the build quality/ parts used, but it shifts great.

There is lots of info on people running synchromesh in Tremec transmissions in various cars. Here's an example:
http://www.teamshelby.com/forums/ind...h-trans-fluid/

This is more about grinding issues, but some good info as well: http://forums.corvetteforum.com/c6-z...t-problem.html

HOXXOH

I do what makes me happy and I expect most others do likewise. The OP asked for advice, so I gave him what would satisfy the requirements of his indicated driving habits. I suspect he'll never keep the car long enough to wear out anything but tires.

BMW charges you for all the "free" services in the initial price of the car. BMW didn't make that investment, you did. It's no different than the warranty on your Vette that was included at "no extra charge" on the window sticker.

JCtx

Don't waste your time with that guy man. He was one of the first in my ignore list .
You're absolutely correct in pointing out brake fluid should be changed every 2 years (at the most), to avoid rusted internal brake components on any car. And like you said, it's the right thing to do, not because you'd have problems during your ownership (most likely not).

Interesting. So the 2011 changes only included carbon blocker rings on 1-2 gears? I thought all synchros were improved as well. Maybe not. And if Pennzoil makes GM fluid, it should also be semi-synthetic then, no? Just curious. I'd like to hear more about Mobil1 tranny fluid (silver bottle, which is the DexIII one). Keep reading great reviews but nobody with an actual TR6060 Vette. Take care.

Streetk14

Obviously the cost of the "free" maintenance is taken into account by the bean-counters. I'm sure you know the lengths the auto manufacturers go to keep costs (and sticker price) down to be competitive and make a profit. It is something they include because they feel it to be important on a high-performance car.




I don't know all the details, but Tremec has made changes to the synchros since the TR6060 became standard on the C6 in '08. I know the newer ones (2010-2011+??) have carbon rings on 1st and 2nd gears only, as well as an updated synchro design. The older ones (like my '08) had no carbon rings at all from the factory.

The GM sychromesh and Pennzoil are supposed to be one in the same. I went with Pennzoil since it's readily available and much cheaper. I want to drain the break-in oil soon, since I've put some miles on the new trans. I'm thinking of going with the Amsoil synchromesh, since it's a full synthetic: http://www.c66racing-synthetics.com/...tins/MTFPB.htm The only thing I don't like about the Pennzoil stuff I am running is that it seems to have higher shift effort when cold. Not surprising really, since it has a higher viscosity than ATF. As a side note, I am not noticing the "marbles in a can" gear rattle when taking off from a stop anymore.

Oh, and I do know Mobil 1 ATF is the only synthetic fluid that's "Approved" by Tremec. The truth is that's the only one they tested, so that is what they officially recommend. I think it's good stuff it you are happy with how the transmission shifts. I don't remember noticing any change when I put it in the T56 that was in my '67. Like you, I like running synthetic fluids when I can.

Just to confuse you more, here is what Dodge recommends for use in the Viper TR6060: https://www.viperpartsofamerica.com/...icant-04874459

Makes you realize there are many different options for these transmissions

C66 Racing

You are partially correct. My 06 CTS-V predates GM's switch to the Dexron LS as does the gear lube study I posted in another thread (the poll). How much difference there is between the old GM diff fluid, which was synthetic, and the new one, is unclear to me. All I really know is the LS has more modifier in it than the old fluid. But, my CTS-V was gen 1 - 400 Hp LS2 engine, so not too far off the LS3 Vette.

Point of both of my posts is that there is actually a lot of variance in how gear lubes perform (the study) and that break-in wear on GM diffs can be significant (the actual used fluid analysis in my CTS-V). Bottom line - I too am a believer in early fluid changes, even if you go back to the factory fill. In my Vette, I changed all the fluids at about 800 miles. We bought my wife a new Equinox a few months ago. Today's project is new fluids.

haljensen

Lots of opinions. Does it really make that much difference which fluid?

My SRT4 (transaxle) used one fluid for both the trans and differential (had to since they are in the same case).The fluid recommended by Dodge SRT Performance was Mobil1 10W40 High Mileage. Yes, an engine oil for the transaxle. The additives in that specific Mobil1 were correct for long wear on the synchros in the trans and suitible for lubrication of transmission and differential gears. No friction modifier needed for the diff, it was a Torsen type gear limited slip.

JoesC5

The Viper stuff; Is this a formula concocted up by Dodge just for the Viper, or is it just a re-labeled brand "????", that meets Dodge's spec's.

JRHAWK9

Below is a thread I started awhile ago over on BITOG.

http://www.bobistheoilguy.com/forums...38#Post1250738

gsflyer2011

I always believed that the Dexron LS was synthetic but thank you for confirming this. Are you saying that Rockland only recommends Pennzoil Synchromesh by brand or just synchromesh fluids in general? (such as RP synchromesh)

At 2000 mile flush (I also believe in flushing out all the break in gunk on new assemblies within a reasonable time) I stuck with Dexron LS for my differential but used Royal Purple Synchromesh for my tranny. The improvement in smoothness was evident on the first drive, and at 4700 miles now, the tranny is simply sweet and keeps getting sweeter. Does not need another shifter or reduced detent modification. To me it is perfect, no grind, no notchiness no noise, positive precise shifts all the time. Like a swiss watch. I do not know how I would improve on it. Or am I just finally (totally bonded with) getting the knack of it?...

JRHAWK9

Just a technicality, but RP's stuff is actually called SynchroMAX

I also have it in my tranny and aside from the cold shifting in cold weather I like the way it shifts.