kcnott

When or how often to change transmission oil in '99 Honda Civic

NVturbo

if in doubt, replace it, especially if you're not the original owner.

Bently_Coop

Automatic or Manual? If Automatic every 30k miles drain and fill three quarts. Honda, Valvoline, Castrol all work fine. If a Manual change when you remove the axles or similar, use Honda MTF only, buy a pump and use the correct fill port. Will take about two quarts if done right.

tony_2018

Check owners manual for specs.

fragmare

~30k miles, same as ignition service interval. Whenever I do a tune up, i always drop 3 qts of ATF and top off. Makes it easy to remember, that way.

SCoupe 5sp

fwiw and imho, 30,000 interval will result in a typical failure in the range of 150,000. Given the rebuild costs are nearly the same as the value of the car, I am going to suggest you do better than book recommendations. The auto fluid "change" is much easier to do than an oil change and can be done at the same time. We have a 2000 LX sedan with 206,xxx miles on the original automatic tranny (that has outlived the orginal motor, saddly enough). I change the motor oil every ~4,000 miles, so at about 15,000 miles, (sometimes sooner) the trans oil gets drained and renewed. The fulid is ok, but clearly nowhere near as clean as the bright cherry red new stuff. There is no way I'd want to see what it looks like at 30,000 miles. The fluid is ~$10 a quart, but I've gotten it as cheap as $5.70 from some online Honda stores. So for $11 to $20 bucks to put a safety margin on the most expensive and nearly terminal part on the car, I think you are well served changing the stuff more often. I also installed an indepentant trans cooler. It is completely separated from the 190 heat of the radiator water coolant based system. Again, ours is over 206,000 and sees 20,000 miles a year and has outlasted the motor.