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Transmission Oil

I have a 1998 Honda Civic (manual transmission) with 108K miles. I have asked my mechanic to change my transmission oil on several occasions and each time he recommends that it is not a good idea. He reason being that when you drain the oil it dislodges a lot of particles that are stuck in the moving parts. The particles are from all the wear and tear that goes on in the transmission. Once the new oil is put in all the particles are suspended in the new oil and can cause damage to the transmission. I asked him if I should ever change the trans. oil and he said probably not. Can anyone offer a second opinion?

Manual transmission fluids last the life of the vehicle. Changing it is unnecessary. However, as long as the fluid is the correct one and the tranny is refilled to the correct level, changing it is harmless. Unnecessary, but harmless.

My Toyota pickup still had its original fluid when it got totalled at 338,000 miles.

Changing fluid in a manual transmission is rare. However, the reasoning the mechanic gave, I believe, typically applies to automatic transmissions. Typically, it applies for when the transmission is old and the fluid has not been changed. If you change it regularly from the start, I don’t think this logic applies. The fear is that removing the fluid will dislodge some particles and cause inferior performance. But again, this is for transmissions that have been mistreated in some way.

You are right. It is often applied to automatic transmissions because they fail shortly after a fluid change. Nearly all of these are from owners with over 100,000 miles on the transmission and had never changed the fluid. Now the owner notices the transmission is not working right and they try the Hail Mary pass and have the fluid changed, then in a few weeks when the transmission does fail, they blame it on the fluid change not on their failure to have changed it 80,000 miles ago.

In most transmission a proper fluid change includes dropping the pan and cleaning it and replacing the filter. Failure to do this can cause all that gunk to mess things up. Same problem can happen with those dual flush services (flush your transmission and wallet at the same time.)

It is time to find a new mechanic. I owned a manual 98 Civic and I belive the owner’s manual says to change the transmission oil every 30,000 miles. That is how often I changed mine. My tranny held 1.9 quarts and I used either Honda manual transmission fluid or synthethc 10W-30 motor oil. Either one will do. Find a new mechanic or change the oil yourself.

This is a pretty easy job to do. It is kind of like a regular oil change except there is no oil filter to change. Basically, you drain it, and fill it with oil until it won’t hold any more. So two quarts should be enough. Make sure you replace the washers on the drain plug and the fill plug. Or better yet, replace the drain plug with a drain valve so you won’t ever strip the threads or replace that washer again.

One of the reasons Hondas last so long is their owners take good care of them. Changing the transmission oil will help this car last as long as it should.

You make a good point about the thinking being for automatic trannys.

For the OP, it’s important to realize the difference…

automatic trannys operate hydraulically, the fluid being controlled an routed through various valves and hydraulic “circuits” and controlling the mechanical portions of the transmission. Free floating particles can get caught up in the hydraulics and cause problems.

Manual transmission use their fluid for lubrication only. There are no “circuits” or valves for particulates to get caught up in. Simply gears in heavy fluid (the viscosity being heavy to withstand the high pressures between engaged gear teeth.

Unless the sytem has been changed, I believe manual tranny uses gear oils, like 85W & up. Automatic tranny uses fluids. I have never heard of changing gear oils in a manual tranny except maybe due to contamination or exposed to elements, etc… which is very rare.