Can You Mix Mercon V with DexronIII/Mercon?
 

When you do a drain and fill of your CD4E transmission in older Escapes (2003 is what have), there is still about 6 quarts of fluid left in the tranny. If the transmission has the older Mercon fluid in it, can you mix this with the newer Mercon V? Or, does the transmission have to be completely drained and refilled with the required amount of the newer Mercon V. I think the CD4E trans flluid capacity is 10 Qts., not sure though.

From what I have heard, Mercon V is thinner in viscosity than the old Mercon, just wondering if this will cause a problem since the transmission is used to the heavier weighted Mercon.

Seems like the experts are stumped on this one!:confused:

Is that correct? A 10 quart capacity and only 4 quarts drains out??

Actually it's 10.1 quarts. When you drain from the "pan" only about 4 quarts come out, the rest of the fluid is in the torque converter and other internal parts of the transmission;

Here is a capacity chart for the Escape:

CAPACITIES:
Engine, with filter..........5.5 quarts [1]
Cooling System, Initial Fill..........10.6 quarts
Automatic Transmission, CD4E Initial Fill..........4 quarts
Automatic Transmission, Total Fill
4 speed CD4E..........10.1 quarts
Manual Transmission, 4WD..........4.7 pints
Manual Transmission, 2WD..........5.8 pints
Differential, Rear..........3 pints [2]
Transfer Case, PTO: 4WD Only..........0.9 pints

Of course there are other ways to drain out your transmission completly besides just draining out the 4 quarts. Some people will disconnect the cooler line going to the radiator, start the engine and add new fluid until you see the new fluid being pumped out. You will use about 12 qts. of fluid doing this.

I used the 3 times fill and drain method which will give you about 85 to 90% new fluid, but then every 15K miles drop only the 4 qts and refill. After about 3 times doing this, your fluid will be just about new. It's the process of progressive dilution. OR, just bring your vehicle to a reputable mechanic or service station or even Ford and have them do a complete drain and refill with new fluid.

MERCON and MERCON V are now fully compatible. Still always a good idea to get as much of the old stuff out, as it is with any fluid.

I've heard that too. There's a TSB out there that states Mercon V is backwards compatible. But I haven't tested that theory yet. I'm still using the Mercon but plan on converting in the future.

It's to risky unless you do like Rancha9 says, drain ALL the old Mercon/DexronIII out of the trans first. I doubt that mixing synthetic fluid with non synthetic fluid is a good idea.

Unless maybe you do the 3x's fill and drain, that might be okay, but still too risky especially on a vehicle like I have with 123000 on the odometer. The seals and internal parts are used to non synthetic Mercon fluid, changing this could cause problems.

For doing the fluid change... From another forum:

Search the internet for: Prowler's fluid change or Prowlers patented fluid change or Prowler's 7-6-3 or 5-5-5... something like that. It's an alternative way to change out the automatic transmission fluid by draining some, adding some, draining some, adding some, etc etc. You might get more search results if you preface your search w site:escape-central.com .

I don't recall the specifics, but I believe a helper is needed to keep topping off the fluid.

yes prowler is or was on EscapeCentral forum for many years, may still be on there. Basically it's simple and I been preaching this on this forum also.