Okay, I was wondering if you were able to find it. And yes, it should last a lot longer than a few months. It actually swells the seal and stops the leak.
As far as replacement, keep in mind it isn't uncommon for a rear main seal to leak a bit with this many miles. If it is minimal, you may want to see how long the additive lasts before replacing it. With this many miles, anything can happen. I wouldn't want to see you put a lot of money into the seal only to have something different and more expensive fail.
Also, if you want to do it yourself, let me know and I'll get you the directions and help you through it.
Take care and if you can, let me know if it helps.
Joe
Friday, October 27th, 2023 AT 8:36 PM