Bought a used 2008 Civic dx sedan automatic with 173k miles for a good mpg daily commuter. So far so good - 34 mpg on two tanks. I am in the process of trying to find service records (previous owners were supposedly Express Oil/Tire Engineers customers). The trans oil is pretty brown. I give it a 7 out of 10 shifting after it's warm. I'm trying to find data supporting whether to change transmission fluid or not. Is there any factual data anywhere?

 

Why not? What's the harm? At least do 1 drain and fill and see how it looks in there (the fluid and the magnetic bolt).

 

I'm just trying to find data supporting whether to change transmission fluid or not. Honestly in a week or so of asking around and reading, it's like a 50/50 - one guy or shop says ohh, better not touch it, there's stuff in that old fluid keeping it together - the next guy or shop says change it and put brand x witch oil in there she'll run better'n ever! Striking out on real research, even finding any so far...

 

Fluid does go bad. You're gonna drive around with the same fluid the life of the car?

And who's the dude that said, "old fluid keeps it together"?

 

old fluid keepin it together.... that's horrible advise.

Change the fluid and hope it was changed at least once before for longevity peace of mind.

 

the guy that runs Ratchets and Wrenches on youtube, whos fairly knowledgable, has given advice about old fluid having clutch particles that is helping a worn out tranny to still be able shift

you hear a lot about people with old trannies having issues shifting after a drain and fill so there is credence to that argument

 

This theory would only be pertaining to an automatic with the wet clutches. However, those same particles that are letting the clutch discs grab are also shredding all the soft parts.

If you do a drain and fill and the tranny starts acting up, it's so worn, it was only a matter of a little time for it to quit completely anyway.

Better to find out now if you have life left in it, then wait for it to quit on you randomly.

 

Also be aware that if you change the oil, your axles seals might start to leak since the new fluid might clean the crud in them.