I could have sworn that my Owners Manual in my 94 Accord said to change the manual transmission fluid every 90k miles, however, the online owners manual and the service repair manual now says 30k miles for manual transmission for my 94 Accord. . Did they somehow change this?

Whats your change interval for manual transmission fluid?

I got the online Honda owners manual here.

I found this post that referenced the 90k change interval:

 

changing fluid clears metal shavings that will clog the trans. that's why the drain plug is magnetic.

 

The recommended service interval is 30k with the current Honda fluid. Obviously if you are racing or beating on the car daily, you should either not be using stock fluid, or be changing more frequently.

 

Is it the current Honda fluid that causes the change interval to decrease from 90k mile change interval to 30k mile change interval?

 

I know the currently fluid is a different formula that what was being used when your car was new, as far as what changes the service interval, I honestly couldn't tell you. Possibly because of a warranty issue.

 

Its a pretty drastic difference. 90k miles, to 30k miles. Same as automatics, however manual transmission doesnt go through the intense beating as what the automatic fluid goes through.

 

I think the 90k interval was for 5w-30 motor oil, which Honda previously recommended for their manual transmissions. Unlike an engine, the environment inside a transmission is not nearly as harsh, there's no fuel contamination or extreme temperature variances, basically just shearing.

The new MTF has additives that improve shift quality but these additives don't last forever. If I had to guess, the 30k interval was designed for the new MTF with these additives to ensure the shift quality remains optimal.

 

Okay, that sounds like a plausible explanation. I did try 10w-30 oil once and had to change it out within 3k miles. I read up about how the old oils used to work back in 94, however the new motor oils since then do not work.