My 2003 civic automatic transmission is slipping. Can I use the Lucas additive, and will it help?

 

No those year 01 to 03 had issues with transmission no additive will resolve the issue ultimately you will need to change the trans. I drive an 01 it happened to me and I got it from Honda Dealer the cost was awesome because they charged me $2800 with 3 year warranty. Hope this help.

 

I take care of a 2003 EX which was really slushy to begin with, I drained it and refilled with the newer Honda DW-1 ATF and 85% of the garbage shifting went away. Been about 12K miles since. The remaining lame laggy soft shifting is just how the TCU is programmed (for eco/emissions, not for keeping the trans lasting a million miles by shifting quick and hard not slipping). So by that I mean the software itself is pretty slippy in my opinion.

The ATF-Z1 (original spec) fluid just sucks. Also DW-1 upgraded my 95 Odyssey and it shifts like some kind of Audi now. Barks into 2nd if it's lightly damp.

EDIT: I changed fluid twice in the Civic, it still looked dirty on the dipstick after the first and some driving. I changed it three times on the Odyssey, and used cheaper Valvoline Multi-Import Syn ATF for the first flush since it was probably loaded with Dexron because obviously if a car exists in America you dump American 1970s ATF in it right? haha

Also check your trans dipstick, the "cork" part of it gets shrunk and it kind of flops around in the hole / can allow contaminant liquids (water, big enough puddle) into the trans. $10 for a new one fixes that issue.