Mercon V vs. Mercon III
 

Anyone know the difference between MERCON V, MERCON III, and MERCON? I've got a '05 EB Expedition, 5.4L V8 with a 4R70/75E transmission (that's what's listed in the owners manual). This is what the manual says:

"Some transmission fluids may be labeled as dual usage, such as MERCON and MERCON
V. These dual usage fluids are not to be used in an automatic transmission that requires use of the MERCON
type fluid. However, these dual usage fluids may be used in transmissions that require the MERCON
V type fluid.

MERCON
and MERCON
V type fluids are not interchangeable. DO NOT mix MERCON
and MERCON
V. Use of a transmission fluid that indicates dual usage (MERCON
and MERCON
V) in an automatic transmission application requiring MERCON
may cause transmission damage. Use of any fluid other than the recommended fluid may cause transmission damage."

If I'm reading this correctly, it looks like I CANNOT use MERCON V (maybe MERCON III as well...) in an automatic trans that requires regular MERCON but I should be able to use a dual usage fluid in a trans that calls for MERCON V, correct?

I'm in S. Korea and asked the post car care center if they carried MERCON V. They looked in their system and said MERCON III is what was listed...I don't really trust them but I'm kind of limited on choices. I would have to try to special order the MERCON V if I can't get it through a local Korean dealer.

Thanks!

Since there's no such thing as "MERC III", that narrows it down.

Ford discontinued Mercon back around 97.

Everything uses Mercon V now that used to use Mercon, regardless of the recommendations made at the time the vehicle was made.

If your vehicle was made to use Mercon and that's all you can get, then it wont hurt anything to continue using a Mercon-rated fluid - you just won't get the benefits of the improved fluid.

Mercon V is synthetic, any other Mercon is not.