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I know our synchros are a weak link, and am keeping that in mind, and might just keep the Honda MT fluid in my car. That said I've had success using Motul and Royal Purple fluids in the manual tranny of some other cars, and have noticed a real difference in smoothness in shifting. Wondered if anyone has used anything long-term that you could recommend that won't hurt the tranny/synchros.

I called Royal Purple, they recommend HPS 5w30.

Some folks on Facebook (maybe here too) are recommending Pennzoil Synchromesh.

Any intel on these or others?

Thanks in advance.
 

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Personally I have been using the Pennzoil Syncromesh in my 2006 MT for the past two years or so- was probably around 245,000 miles when I changed it, currently above 265K. My transmission already had the downshift grind in 2nd gear when I bought the car, and fresh fluid won't fix that of course, but it did make it a good bit less stiff going into gear in the winter cold. Besides that so far so good. I intend to replace the transmission with a rebuilt one sometime in the next couple of years but for now it's perfectly usable with double-clutching.
 

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Just put fresh Honda MTF in and be happy.

I used to have a 2004 Honda Civic Hybrid 5MT. At one point I noticed that when it was cold out (below freezing), the shifting would become quite stiff. It really didn't like going into 2nd and especially 1st gear while moving. I put fresh Honda MTF in, and that fixed the problem.

The synchro issue on 1st and 2nd is a design weakness/limitation of this transmission. No amount of magic bug juice is going to prevent the issue. You can mitigate it by not slamming it into first or second at higher speeds. Probably 15 and 30 MPH respectively.

Also, learn how to double clutch if you don't already know how. It's simple and useful to know when you need a low gear at higher speeds and want to take it easy on the transmission.
 

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Just put fresh Honda MTF in and be happy.
...
The synchro issue on 1st and 2nd is a design weakness/limitation of this transmission. No amount of magic bug juice is going to prevent the issue.
I disagree, as do the other engineers and SAE certified master mechanics in my family. There are better fluids that bean counters haven't cheapened or compromised for high mpg figures. Some fluids will prevent damage including future damage on a partially worn component.

Not that you said this, but there are others who scream "Why would anyone EVER use something other than the OEM recommendation for fluids or parts? Reee!" and the answer is the same. They're designed to a price point and service life to fit within the warranty period. Aftermarket parts/fluids can be worse, similar, or significantly better.
 

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I stopped by the Honda dealer today, thinking I'd pick up a couple quarts of MTF. It was like $12-13 a quart. Call me crazy, but that seemed way over priced and I said, no way...

I can't help but think that any transmission oil is likely to do about the same as any other. Whether one 'shifts smoother' than another, will it really be such a difference that I'd notice and care? They'll all offer basic protection, won't they?


edit: WTF? I just went to amazon, looking for AC delco syncromesh, and that's even more $ than the Honda MTF at the dealer. And I also saw Honda MTF there and it was like $16-17 a quart... Has MTF always been that expensive and I'm just forgetting that? I just bought 5 quarts of Mobil 1 motor oil for like $22 ($4.40/qt) - why is MTF so much more expensive - it's more than 3 times the cost?
 

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way over priced and I said, no way...
That's ok for fully synthetic, but there are better fluids for Hondas, especially a 1st gen Insight.

I can't help but think that any transmission oil is likely to do about the same as any other. Whether one 'shifts smoother' than another, will it really be such a difference that I'd notice and care? They'll all offer basic protection, won't they?
I noticed a difference even between new fluids, not just old to new, and I was skeptical. I think you'll notice a difference too. No, they don't all protect as well as each other, just like engine oils.

Has MTF always been that expensive and I'm just forgetting that? I just bought 5 quarts of Mobil 1 motor oil for like $22 ($4.40/qt) - why is MTF so much more expensive - it's more than 3 times the cost?
You almost never change it, so really it isn't too bad. Economy of scale is a factor, plus it's different stuff and has to survive shearing the molecules in ways that engine oil doesn't (except engines with a shared transmission like Japanese motorcycles). Plus everything has skyrocketed as hyperinflation is setting in, despite what talking head economists tell you on the boob tube.
 

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You almost never change it, so really it isn't too bad. Economy of scale is a factor, plus it's different stuff and has to survive shearing the molecules...
Yeah, I realize that, it just seemed way more expensive than I remembered, or compared to motor oil. I think I just forgot that MTF is more expensive... I think I'm gonna have to go back to that dealer - from looking around online, $12-13 is actually a good deal.
 

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Yeah, very few people have manual cars and even few of them actually change their fluids so it's pretty rare. Almost everyone actually changes or has their oil changed regardless of what transmission they have.
 

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Yeah, I realize that, it just seemed way more expensive than I remembered, or compared to motor oil. I think I just forgot that MTF is more expensive... I think I'm gonna have to go back to that dealer - from looking around online, $12-13 is actually a good deal.
Yeah. Local GM shop here got me 2 quarts of the good stuff for $25, and I was happy with that.
 

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The funny thing is, after I went back to the dealer and bought a couple quarts, and changed the MTF, I had like ~12oz left over. Which made me think: What happened last time I changed it? So I looked underneath some junk in my garage and found a bottle that was more than half full, i.e. I could have gotten away with buying only one quart, and saved $12. Let's see if I remember next time, some 6 years from now...
 

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Been there, done that!😊😊
 

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Personally I like Redline MTL. I put some in my Insight and although I can't claim the shifting is worlds better, it seems to be the general consensus that no fluid is going to do that on a tired insight transmission. That being said I don't have any issues getting my insight into gear, it just can't be rushed unlike other cars. I've had great experiences with MTL in BMW manual transmissions, it seems to bring those right back to life to the point where you can bang gears until the rear subframe gives out or something else breaks ;).
 
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