Had a shop put Amsoil in my 4R70W about 80K miles ago. Proobably should have changed it before this, but I didn't. Still topped off I might add, and according to the auto-meter trans guage it never overheats. I'm going to do a drain and fill in the next couple weeks (no flush). Think it would be OK to just go with the off the shelf stuff, and have it mixed in? Or should I find a dealer and go with the Amsoil? Truck has 151K miles on it, and will be sold or traded in within six months. The other option is to just leave it and let the new owner deal with it, but I have a few more camping trips this summer towing the RV so I thought it might be a good idea. Thanks,

 

Mercron V is synthetic so I would just put it back in there.