This first post has been completely rewritten as I originally tested only one fluid and the testing snowballed a bit. Now that I have a fluid combo i'm happy with, i'm not doing another fluid change. I've done four of them and that's enough for now. Ultimately, i want to provide my impressions of what I found about my 2010 Accent GS transmission. Keep in mind all this was done with only a couple thousand miles on the odometer of a new car. Perhaps "broken in" transmissions would behave differently.

Recommended Fluids:

• RedLine MTL 70W80 (I mixed it approx. 10:1 with a bit of Hyundai 75W90. It MIGHT be OK to use straight MTL)
• RedLine MT-85 (not tested, but should have similar properties to the MTL/75W90 mix above)
• Stock Hyundai 75W85 Fluid, PN 08950-00020-A (imagine that )

I had to mix the RedLine MTL as i ordered 2 quarts and didn't have any fluid coming out of the fill hole when i pumped all of the MTL in. Ended up adding a few ounces of the Hyundai stuff to top it off. Since the MTL and the MT-85 are fairly close in viscosity, AND i'm quite happy with my MTL/75W90 mix, i will not be testing the MT-85. I ordered it, it's on my shelf. I will put it in in four years when i'm supposed to change fluid again I just hate wasting more fluid just for the heck of it. Given my tests, i'm pretty sure the tranny will be happy with the MT-85. Also, RedLine specifically lists this fluid as OK for my Hyundai, based on the Hyundai PN they provide. Maybe another reader on here can chime in one their experience with MT-85.

Tested Fluids That I Consider Marginal:

• Hyundai 75W90, PN 08950-00010 (doesn't have sticky gears when cold, but the shifts feel pretty bad when cold.)

Tested Fluids That Are NOT RECOMMENDED:

• Amsoil 75W90 MTG ("sticky" shifting when cold. Similar to stock when warm)
• RedLine MT-90 (Also sticky when cold. Shifted better than Amsoil when warm though.)

You might see a pattern in the above... Seems that the thinner tranny lubes work best. The manual calls for 75W85 for a reason I suppose. Amsoil claims its 75W90 is OK for a car needing 75W85, but I disagree. It happened to be the first fluid I tried and I got rid of it quick. In the case of my Accent tranny, it was awful when cold. By cold, i mean 40F overnight temps. Not Canada cold... just California cold. I liked the RedLine better when warm, but it too suffered from very sticky shifting when cold.

Here's the sequence i tried the fluids in, in case you want to consider contamination from the previous fluid in your evaluation of my findings:

1. Hyundai 75W85 (put in at the factory)
2. Amsoil 75W90 MTG (garbage when cold)
3. RedLine MT-90 (garbage when cold)
4. Hyundai 75W90 (not sticky when cold, but very rough shifting until warmed up)
5. RedLine MTL with some Hyndai 75W90 mixed in. (A bit rough cold, very nice warmed up)
6. RedLine MT-85 (not tested yet. Likely identical to MTL/75W90 mix I have in now).

If you look above, i kept going from one fluid that didn't work to another. I finally drifted back to lower viscosity stuff that seems to work well. Now, it won't make the tranny "like buttah" all the time. I find my trans can be finicky. Sometimes its very smooth, sometimes not, even with the RedLine stuff in. My overall impression is that the MTL or the MT-85 from RedLine provide overall better shifting than the stock fluid. Just don't expect miracles. It's not a BMW trans. Those do shift "like buttah."

Hope the above will save you some money and time. Extra info and extra "homework" below:

Below i've attached a table i made of synthetic GL-4 lubes available from RedLine and Amsoil. You can see how the MTL and MT85 are close at 40C, while the 90-weight lubes are quite a bit thicker. At 100C, which the trans will likely never see, they're pretty close in viscosity. The oil i've drained from my tranny has always been quite warm after driving, but never burning. I'd estimate that it was approximately 40C when warmed up, so the viscosity info at that temp is pretty nice to have. I've also included part of the SAE J306 viscosity standard, which specifies viscosity ranges for gear lubes. I'm including the 100C viscosities only, as viscosity at 40C is typically only used to calculate viscosity index and not the viscosity rating of the oil. If you want to find out more, read about viscosity on wikipedia and read up on SAE J300 (motor oil) and J306 (gear oil).

 

first thing to note is that the manual in the accent is not the smoothest shifting, never was never will be. it is, however, reliable. just a little cranky at times.

my experience has been vastly different. i switched to amsoil 75W-90 GL-4 full synthetic and i'll never look back. all around better, shifts smoother and accelerates slightly faster. same with cold weather, and i'm in canada so u know it gets pretty chilly.

so if the hyundai stuff works for you, keep it. why not, it works. however, i wouldn't say 'don't waste your money' to everyone, most people i talk to love the synthetic in the gearbox. why yours was cranky with it, i don't know. a GL-5 will make it behave like ***, but u did the right thing in using the GL-4. same for the oil weight, but yours looks right in line.

one final thing: i don't know what the oil recommendations are for the 2010 accent (i have a 2004) but i'd double check that 0W20 out...its never a good idea to go outside of the recommended oil synthetic or not. that stuff is pretty thin.

 

I just want to give people information, so that they can make a better-educated decision on how to spend their money. I feel like i wasted mine in the case of my new Accent. I like the car and all, but the tranny didn't seem to "respond" to synthetic treatment. I still plan to use synthetic in the engine, but will stick to the OEM stuff for the trans. If the shifting was as bad as it was at California temps, i'd be afraid to see how it behaved in the colder north.

I've had positive experience with my old Honda CRX (as mentioned above) using RedLine MTL, as well as two different Honda motorcycles (some other synthetic, don't recall). When i switched to synthetic, the shift effort went down noticeably. This just wasn't the case with the Accent tranny. Warmed up, differences were minor. Cold, pure garbage.

Using GL-5 would have been a bad idea, as the additives to some GL-5 lubes will eat the tranny components. I believe it's the sulphur additive affecting brass synchro components, if memory serves.

 

Better look at the label on the back of the Hyundai bottle you bought..

The only GL-4 M/T oil Hyundai sells is 08950-00020 (75/85)..

If the oil you bought came in a grey bottle with blue label, look at the small print on rear label, it is GL-5... NO NO according to instructors at M/T school...

Got part number for the Hyundai stuff you installed.

 

Mine is a white bottle, white label. Looks very similar to yours, except it's part number ...00010 and it says 75W90 on it. Might have been old inventory or something. Of course, my local dealer wouldn't just try to dump old stock on me now would they. That would be unethical Don't really think it matters much either way. Been driving it more and the tranny still isn't as smooth as i'd like with the stock fluid. It's still better than the other two i tried when the tranny is cold, but not as good as i'd like.

 

Ok, my first post totally rewritten. I've put several hundred miles on the RedLine MTL and i'm leaving well enough alone. I like it. I updated my findings above. Hope the time and money I spent prevents others from doing the same. All I wanted was a smooth trans dammit

 

If you ever change it again, switch to Royal Purple. I use it in all kinds of equipment from 1180hp nat gas engines, gear boxes, compressors(nat gas and air), air tools, and small engines. I had a large piston water pump that cracked the crank case and lost most of the oil, of course the low level shut down failed to stop the pump, but even with the small amount of oil left in it damage was kept pretty minor.

 

sigh....here we go again. pick your poison and be happy with it. kind of like hard liquor.

 

Yes sigh, another from zero the hero. My engines are bigger than the room you rent in your parents basement...

 

coming from the guy who has been so helpful around here...they have been a really excellent 12 posts!!

P.S. i own a home and an apartment, would you like to rent from me?