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Beach bumming it ........
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91 351w E4OD


Would it be ok to mix these two:

Castrol Transmax Mercon V





CARQUEST Oil & Fluids Dexron III/Mercon (ATF)



This is probably a dumb question. I am going do a transmission fluid/filter change tomorrow and I currently have 6 quarts of Castrol Transmax Mercon V and 4 quarts of CARQUEST Oil & Fluids Dexron III/Mercon (ATF). Both say they can be ran in my truck I just don't know if I can mix them.

I was thinking it would save me money if I could use these together.
 

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Steve's going to come in here and tell you to dump it all out and buy Motorcraft fluid.
 

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Some good info in the thread below. Personally I don't think that it would be an issue to mix them, but I wouldn't. I would stick with Merc III if it were me, and it's cheaper since I am pretty sure Merc V is synthetic.

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=526269
There's no such thing as "Merc III." It's just regular "Mercon" which is the same thing as Dexron III. Mercon V is not necessarily synthetic. There are synthetic Mefcon V products out there, but there are also syn blend or conventional Mercon V fluids. I tried searching to see if the Catrol fluid is synthetic, and didn't find any info on it. Even if it was, you can mix it with a conventional fluid just fine.

You can mix the two fluids and nothing bad will happen. I would do it without thinking twice.
 

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There's no such thing as "Merc III." It's just regular "Mercon" which is the same thing as Dexron III. Mercon V is not necessarily synthetic. There are synthetic Mefcon V products out there, but there are also syn blend or conventional Mercon V fluids. I tried searching to see if the Catrol fluid is synthetic, and didn't find any info on it. Even if it was, you can mix it with a conventional fluid just fine.

You can mix the two fluids and nothing bad will happen. I would do it without thinking twice.
Yes, I was referring to the Dex III/Merc mix commonly found on shelves, but if you want to get technical Dex III and Mercon are not the same fluid.

And I'm pretty sure that all Mercon V is at least part synthetic.
 

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yo,
Ford Customer Service Division's Motorcraft Chemicals and Lubricants U.S. Catalog
MERCON V
 

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Why wouldn't you be able to? If both fluids work in a system then there you go. It's not like there's going to be a chemical reaction that turns all the fluid into raw sewage. You think they'd go around giving lawsuit bait advice about being a 'compatible' fluid for transmissions? Transmissions are nearly impossible to drain completely, there's ALWAYS *some* mixing going on.
 

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It's fine.
 
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