What is the best additive to put in your transmission to make it last longer?
Replace the transmission fluid regularly. Depending on the car, the recommended mileage may be never to 30,000 miles. I'd change it at least every 50,000. Additives aren't needed. If you are having an issue, you may need to take it to a mechanic. You can try some of those additives if it is slipping, etc., but I wouldn't hold my breath that it will fix it.
The best way to make it last is to replace the fluid every 40k-50k miles, use synthetic even if it's not required don't use any additives.
Nothing. Just fresh transmission fluid.
