Can you mix Mercon and Mercon V?
 

Can you mix MERCON and MERCON V together? I had my trans flushed last week and want to change the trans filter now. The dipstick on the trans says use MERCON and when I took it in to Firestone to get it flushed the guy told me I needed MERCON V (a synthetic). The receipt does not say what fluid was put in.

Can they be mixed? If not, how can I tell what was put in without flushing the whole system again?

Thanks

Mercon V is not, by specification, synthetic. It is usually a hydroprocessed blend that is Dexron/Mercon/Mercon V. Unless you have an E4OD that specifically prohibits Mercon V, you are fine. Since you have a 4.6 4x2 F-150, you dont have the E4OD. There should be no worry about mixing Mercon fluids in your case.

GM has an ATF spec that is backward compatible to 1949. Why does Ford, and worse, DaimlerChrysler with "dealer only" +4, have to make it so complicated?

Jim

:) Thanks, it's good to know that I'm OK either way. The trans is a 4R70W. I'll change the filter tomorrow after work. Thanks again.

Originally Ford recommend using "Mercon" in the 4R70W out of the factory right up until 1997. That is why it's written on your dipstick. Beginning in 1998, "Mercon V" became the standard for that tranny.

However, I'm pretty sure that the Ford tranny guys changed their tune a few years ago and determined that "Mercon V" should now be used in the 4R70W tranny for ALL years. So maybe Firestone was actually on top of things by telling you that.

Here is the source of my information about all 4R70W trannies now requiring Mercon V:

Tranny Fluid for the AODE-4R70W

Thanks Rockledge fir the information and followup. Used the Mercon V when changing the filter.

General rule of thumb is that the upgrades are typically safe, just the newer version. Usually you can upgrade an older trans to the newer stuff, just don't try to put older oil into an newer trans, (like if you had a stockpile of it) Only exception is the older Type F tranny's, but then that's why it says type f, not Mercon.

Just dont try to put Mercon in a trans requiring Type F. Your intermediate band will go bye-bye in a big hurry. Trust me, I learned the hard way.

You don't really want to use Mercon V in an older AXODE/AX4S tranny, either.

On the other hand, you should be adament about using it in one built after '97.