Automatic Transmission additives

Hi, I am a new member.I have a subaru Forester with 49000 miles on it. I will be performing my second ATF change using Pennzoil dextron 3. I drain the fluid refill it drive 5 miles or so and drain and refill it again. My question is does anyone use and think transmission additives like Wynns or Lucas products are worth using. Some subaru dealers push them.

I don’t think additives will help that much. But a good synthetic trans fluid will.


Additives can be good. All my rebuilds leave the bench with a bottle of Lube-Gard red in it. There are several Lube-Gard transmission products availiable. Use the one in the RED bottle. It is a conditioner. A majority of transmission guys I know use this product in regular servicing.


There is no particular reason that you should drain and fill after 5 miles. It would make just as much sense to cut the service interval in half.

I agree with not draining it twice in the same day and just reducing the interval. Additives can make a bad transmission quit working altogether. A good one may never need additives.

I thought draining the atf fluid twice in the same day would get most of the bad fluid from the torque converter. Should I cut the change interval down from 25000 miles to 12500 miles ?

Thanks for the reply, Do you think semi synthetic ATF is a good idea? I am thinking that it would mix easier with the conventional Dextron 3 that is residually left in the transmission when it is drained.

Go to and search on “Lucas.” There is a good writeup of an experiment adding Lucas transmission treatment to a couple of different automatic transmission fluids. It appears that the addition of the product resulted in considerable air entrapment in the fluid which caused the color to change to a milky yellow and would, presumably, reduce the lubricating ability of the fluid.