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Amsoil Synchromesh or Amsoi 75W-90 GL4 (6 Speed MT)

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75w90 amsoi amsoil general question gl4 maintenance speed synchromesh transmission
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xMOWERYx

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Discussion starter · #1 ·
Hopefully this thread hasn't been repeated multiple times. I only visit the site when looking for answers or opinions, so I'm not sure if this thread has already been discussed.


(For those who don't feel like reading this unintentional book, I need Pros and Cons between the two Amsoils and any other feedback about changing oil etc.)




I have the infamous 2nd and 3rd gear hard shift problem. I have right around 37xxx miles right now, so It's about due for a fluid change. I'm the second owner of this car, so I can't really be sure how rough the previous owner was. Never really grinds the gear, just a little rough going in. Happens most often when car is cold. Funny enough it shifts better in colder weather when RPMs are around 3000. Not really a good thing though. Terrible for fuel mileage.

I am in the process of trying to decide what kind of fluid I want to go back into my transmission and I was wanting to gather as many opinions as I could before changing it, since it will most likely be in for a few years.

I drive mostly highway probably 75%. I live in Missouri, so I have the miserable 100+ heat and the frigid freezing winters. So I need a versatile fluid that won't gel up. Today's high was 15 degrees Fahrenheit and the shifting was quite clunky.

From what I hear, Amsoil is probably the best way as far as tranny fluid. I do know that I could void my warranty if I have a lubrication failure, but I figure if I have to take my car in for any transmission work, I will just put new fluid in that is GM approved beforehand.

I do enjoy a lead foot every now and then, but mostly stick to economic driving. I'm tempted to put in the more high performance Amsoil, but I'm afraid it will be too thick for the winter.

Anyway I appreciate any and all feedback. I plan on changing it the next time I'm due for an engine oil change.
 
#2 · (Edited)
For no reported grind and smoothest shifting in the teens and single digits, synchromesh is probably a better bet. Your driving doesn't really merit the 75W-90.

Both of those fluids won't gel up till way past -50F. They'll just slowly get thicker. In fact, the 75W-90 thickens less than the Synchromesh past -30F, but is thicker up to that point. It gets a bit stiffer getting into gear for me any time it gets below 20, but fine up to that. I've used both in winter and summer. The 75W-90 shifts just fine after you drive a block or two. Just first few shifts on a cold morning can be a bit stiff.

I'm keeping the 75W-90 in there just because I like to overcompensate when it comes to lubrication.

Shoot me a PM if you want pricing.
 
#3 ·
Use the Syncromesh. I'm currently using the 75-90; My 1-2 shift gets a little clunky first thing in the morning around 40F and REALLY does not like to go in under 20. That said, I can't recall ever grinding the 1-2 shift on this fluid like it did with the Synchromesh.

Some transmissions seem to have 1-2 trouble more than others, and probably what my cars deal with it is. I did notice that letting the car idle up to 85F before setting off made the fluid a lot less stiff even though it was just in neutral.
 
#4 ·
I use Amsoil Synchromesh in my ECO and it's a bit stiff at 10f or less but mine never grinds and I don't have any issues with 2-3 shift either. You might want to use Synchromesh and also check the cable adjustments. If they aren't adjusted properly it can do exactly what you described. The previous owner may have abused the shifter a bit. Mine has 75k and shifts like new. I've driven others that have been abused and they can be notchy and difficult.
 
#5 ·
I'm using AMSOIL synchromesh in my ECO MT. Denver temps mirror yours.
 
#6 ·
I have a 2012 CRUZE with Manual. After doing a long time search and calling the dealer, I was told in places with hot summer (+ 100F) it is recommended somewhere between 30K-50K miles. In places not so hot, it can go longer time.
Also, I tried to find a good Synthetic one, for my car but after contacting AMSOIL, I was told "there is no AMSOIL product matching the GM part number 19259104 which is W70.
Not sure, just for being mono-grade or there is another reason.
Of course the only thing I am 100% sure, is the fact, our M32 transmissions are synchronized ones and need SYNCHROMEH oils.
In case anybody have used the AMSOIL SYNCHROMESH for a considerable number of months or mileage, would you please, add a comment about it. Did you feel any improvement. Any possible damage to transmission.

Thanks.
 
#7 ·
CRUZIFIED said:
I have a 2012 CRUZE with Manual. After doing a long time search and calling the dealer, I was told in places with hot summer (+ 100F) it is recommended somewhere between 30K-50K miles. In places not so hot, it can go longer time.
Also, I tried to find a good Synthetic one, for my car but after contacting AMSOIL, I was told "there is no AMSOIL product matching the GM part number 19259104 which is W70.
Not sure, just for being mono-grade or there is another reason.
Of course the only thing I am 100% sure, is the fact, our M32 transmissions are synchronized ones and need SYNCHROMEH oils.
In case anybody have used the AMSOIL SYNCHROMESH for a considerable number of months or mileage, would you please, add a comment about it. Did you feel any improvement. Any possible damage to transmission.

Thanks.
Click to expand...
The reason why AMSOIL doesn't have a recommended fluid is the following:

AMSOIL Synchromesh is one viscosity grade thicker, and is considered a GL-3 gear oil as it has fewer extreme pressure additives.
AMSOIL 75W-90 GL-4 MTF is a 85/90 weight oil, which is two viscosity grades thicker than the OE oil and can shift a bit clunky in the extreme cold for the first few shifts, but has the correct GL-4 rating and also works well. In short, neither match the OE specification perfectly, which by the way has gone through three formulations. That's right, GM used 3 different part numbers for 3 different fluids in the Cruze M32.

That being said, this is the option that the community has noticed provides the best results after trying a variety of others, and the fluid costs 1/2 that of the OE fluid.

I've sold over 200 changes of this manual transmission fluid to Cruze owners and not one has reported an issue. We had one member push it to IIRC 78,000 miles, and while there was some viscosity shear, it was not severe and there were no alarming wear levels. So far, there has not been a single failure that I am aware of in our transmissions after extended use of these fluids. I've been using them since 2013. I first change it at 13,500 miles, trying Synchromesh first, and then switched to the 75W-90 GL-4 MTF at 37,755 miles. I am now at 59,000 miles.

There is an across the board improvement in shift quality, with many reporting that their 1-2 shift grind was eliminated (if existed). The only thing I would caution you on is the 75W-90 GL-4 MTF. It can be a bit stiff going into gears on a very cold morning. I usually let the car sit for about a minute with my foot off the clutch pedal on a cold start, and after about 3 shifts, everything smooths out. It is a thicker fluid, but is very nice in the warmer months. Your location says California, so I would run straight to the 75W-90 GL-4 MTF.

That being said, this is what I have seen from my own customers.
 
#8 ·
I saw the pic and wondered how did you get my car! LOL Same year color etc. I have a similar issue going into 3rd and I found it was more than not bc I moved my seat and not pressing my clutch in all the way. My problem is a little grinding downshifting more than not or into speed shifting. I am due for a fluid change also as I am at 66K and want to check out Amsoil also.
 
#9 ·
I've had the Amsoil manual synchromesh (thinner grade) in mine for the past 37,000 mi. and see no sign of harm. There's enough R&D with it now that I have no apprehensions about using it or recommending it be used. Whichever grade you use, the sooner you change from the factory fill the better.
 
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#10 ·
I've been using the AMSOil Synchromesh now for 40,000 miles. Shifting hasn't deteriorated this entire time and I still don't grind my 1->2 high RPM WOT shift. I am running a little low (2 qts vs. 2.5 qts) because of GM's original 2 qt spec for this car.
 
#11 ·
XtremeRevolution said:
The reason why AMSOIL doesn't have a recommended fluid is the following:

AMSOIL Synchromesh is one viscosity grade thicker, and is considered a GL-3 gear oil as it has fewer extreme pressure additives.
AMSOIL 75W-90 GL-4 MTF is a 85/90 weight oil, which is two viscosity grades thicker than the OE oil and can shift a bit clunky in the extreme cold for the first few shifts, but has the correct GL-4 rating and also works well. In short, neither match the OE specification perfectly, which by the way has gone through three formulations. That's right, GM used 3 different part numbers for 3 different fluids in the Cruze M32.

That being said, this is the option that the community has noticed provides the best results after trying a variety of others, and the fluid costs 1/2 that of the OE fluid.

I've sold over 200 changes of this manual transmission fluid to Cruze owners and not one has reported an issue. We had one member push it to IIRC 78,000 miles, and while there was some viscosity shear, it was not severe and there were no alarming wear levels. So far, there has not been a single failure that I am aware of in our transmissions after extended use of these fluids. I've been using them since 2013. I first change it at 13,500 miles, trying Synchromesh first, and then switched to the 75W-90 GL-4 MTF at 37,755 miles. I am now at 59,000 miles.

There is an across the board improvement in shift quality, with many reporting that their 1-2 shift grind was eliminated (if existed). The only thing I would caution you on is the 75W-90 GL-4 MTF. It can be a bit stiff going into gears on a very cold morning. I usually let the car sit for about a minute with my foot off the clutch pedal on a cold start, and after about 3 shifts, everything smooths out. It is a thicker fluid, but is very nice in the warmer months. Your location says California, so I would run straight to the 75W-90 GL-4 MTF.

That being said, this is what I have seen from my own customers.
Click to expand...
In my case, there was an unbelievable difference between the 75w-90 and Synchromesh, the 75w-90 being the far better of the two to drive with. Much smoother gear transitions.

Even with this winter touching single digits and teens a few times, it wasn't too bad to drive - the 1-2 and 2-1 shifts are clunky for about 1 minute.
 
#12 ·
XtremeRevolution said:
The reason why AMSOIL doesn't have a recommended fluid is the following:

AMSOIL Synchromesh is one viscosity grade thicker, and is considered a GL-3 gear oil as it has fewer extreme pressure additives.
AMSOIL 75W-90 GL-4 MTF is a 85/90 weight oil, which is two viscosity grades thicker than the OE oil and can shift a bit clunky in the extreme cold for the first few shifts, but has the correct GL-4 rating and also works well. In short, neither match the OE specification perfectly, which by the way has gone through three formulations. That's right, GM used 3 different part numbers for 3 different fluids in the Cruze M32.

That being said, this is the option that the community has noticed provides the best results after trying a variety of others, and the fluid costs 1/2 that of the OE fluid.

I've sold over 200 changes of this manual transmission fluid to Cruze owners and not one has reported an issue. We had one member push it to IIRC 78,000 miles, and while there was some viscosity shear, it was not severe and there were no alarming wear levels. So far, there has not been a single failure that I am aware of in our transmissions after extended use of these fluids. I've been using them since 2013. I first change it at 13,500 miles, trying Synchromesh first, and then switched to the 75W-90 GL-4 MTF at 37,755 miles. I am now at 59,000 miles.

There is an across the board improvement in shift quality, with many reporting that their 1-2 shift grind was eliminated (if existed). The only thing I would caution you on is the 75W-90 GL-4 MTF. It can be a bit stiff going into gears on a very cold morning. I usually let the car sit for about a minute with my foot off the clutch pedal on a cold start, and after about 3 shifts, everything smooths out. It is a thicker fluid, but is very nice in the warmer months. Your location says California, so I would run straight to the 75W-90 GL-4 MTF.

That being said, this is what I have seen from my own customers.
Click to expand...


Thnaks XtremeRevolution, for the really good information. I think, I will go with the one you mentioned. I drive mainly in Sacramento area or South Cali with above 100 degrees in summer.
 
#15 ·
You're welcome.
 
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