What ATF is used in a 2001 Lightning now that Mercon is no longer available.

 

Mercon uses a high VI conventional base oil. Mercon V uses a Gp III or synthetic base oil. The V is a little more stable over the long haul. The formulation also addresses torque converter shudder that was an issue in your truck. Mercon is still made by lots of makers. Motorcraft has never made any lube products. Its always been made by various others to Motorcraft specs. Using a brand such as Pennzoil, Castrol, or Valvoline is not a negative vs Motorcraft labelled ATF. You can also use ATF meeting Dex III, which pretty much mirrors Mercon. I'd suggest Mercon V made by any quality name brand.

 

Thank you for the info and help

 

You can still get Mercon from folks like me that squirrel away stupid crap like discontinued fluids, oil filters, Liquid Glass, lol. Look on eBay.

Would I be concerned using Mercon V? Absolutely not.

 

Castrol makes a Dexron/Mercon trans fluid. I just bought some at Autozone.

 

I have a full billet built 4R100 and I use dex/merc rated with good results. Before the build I used synthetic, but the builder said to use regular mineral fluid and change it every 10000-15000 miles.
It is as important to get the grime out as it is to use good oil. Synthetic is an extra expense when you change it that often.