Difference between Mercon and Mercon V Transmission fluids? | Ford Explorer Forums - Serious Explorations

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Difference between Mercon and Mercon V Transmission fluids?


Explorer Addict
April 17, 2011
Reaction score
City, State
Orchard Park, N.Y.
Year, Model & Trim Level
'05 Explorer XLT 4.0L
Does anyone know if "Mercon" transmission fluid is the same as "Mercon V" transmission fluid? Any differences in the fluids? I was at Advance Auto Parts yesterday and I had the clerk there lookup in their system, what type of transmission fluid my 2005 Ford Explorer V-6 uses in the 4x4 Transfer Case. Advance Auto Parts says my vehicle uses Mercon V, but my Haynes manual says it uses plain Mercon ATF. I told the clerk this and he said plain Mercon was the older type of Ford transmission fluid and it was replaced by the newer Mercon V. Advance carries both types of transmission fluid. They carry the Dex/Merc which is plain Mercon ATF and the Mercon V ATF. I was looking at topping off my transfer case with fluid if need be and just want to be sure to use the correct transmission fluid. The clerk said to go with Mercon V. Can anyone clarify any differences between the fluids besides the label names? Thanks in advance for any help with this!

Read here: http://www.imakenews.com/lng/e_artic....cfm?x=b11,0,w

Or here:http://www.explorerforum.com/forums/showthread.php?t=166085 (same article).

The article is from '06. I recall reading that Mercon V is partial synthetic.

And here's a FAQ from this website:

Q4. What is the difference between Mercon III and Mercon V beside price?Can I substitute MERCON III in place of Mercon V and save some $$?

A4. Mercon is the designation FORD gives to their requirements for ATF performance. While we tend to think of OIL as OIL.... Pennzoil 5-30 can be mixed with Quaker State 20-50 for example.... ATF is not all the same.

The simple answer is, if your transmission callsfor Mercon V... you cannot subsititute Mercon III. Mercon V has some special "friction qualities" that Mercon III does not. If the manual says use Mercon V, use V.

CAN you substitute Mercon V for Mercon III backwards? Yes, but Mercon V is way more expensive, so why?

Q5. My shop used Mercon III and an additive instead of Mercon V. Am I screwed?

A5. No, and kinda. Mercon III is not synthetic, at all. Synthetics have some advantages in terms of temperture stabilitity and longevity. Mercon V is "semi synthetic". (Not as good as full synthetic, but better han non-syn). It IS possible to add a special additive to make Mercon III mirror the friction qualities of Mercon V.

Is this an accepted practice? Yes. Is it safe? yes. Is this as good as using Mercon V to start with? No.

If you have a transmission using Mercon V (basically anything 96-97 on) and you are going to have the fuild replaced... ask if they will use native Mercon V or just Mercon III with an additive. Mercon V is the better choice.

Q5. OMG I accidentally mixed a quart of Merc III into my Merc V tranny. Am I in serious trouble?

A5. No. relax. The main difference between III and V is in two things. V is a mixture of synthetic oils and naturally occurring oils. Is syn better?yeah. Is semi syn better,? half yeah. Merc V has friction additives lacking in III. Is a 10% dilution factor gonna matter? no, not much.

The base stocks of ATF, like the base stock of oils, are interchangeable. Mix and match.

No it will not gel, not it will not thin, no it will not cause a spontaneous fire. And no one will die. RELAX.